A little more than a week after the shooting rampage at Pulse, an Orlando nightclub, key details remain unknown about what exactly happened during the violent episode and the hostage standoff that followed.
Even as investigators try to determine what may have motivated the attack that left 49 people dead and dozens more injured, they are still working to piece together exactly what happened during the three hours between the first gunshots and the moment police fatally shot the attacker.
Authorities have not said yet if any of those killed or injured at the club were wounded when police officers fired at Omar Mateen, the 29-year-old gunman, something police have said was possible, or when police SWAT teams tore through the walls of the bathrooms where people were hiding.
The FBI is still working to determine if any of the victims were hit by police fire, according to a US law enforcement official who spoke on the condition of anonymity to discuss an ongoing investigation.
The official said it may take as long as a week, and possibly longer, before authorities are sure.
As part of this effort, agents are reviewing graphic surveillance video from inside Pulse, which the official said clearly shows Mateen gunning down victims.
Investigators have said that their evidence response technicians remained at Pulse for days after the shooting to map the crime scene and try to determine precisely how the bullets flew as they analyze the trajectory of the gunfire.
When police made the decision to go inside at about 5am to end the standoff, officers assumed there were "badly wounded" people in the club still needing to be rescued, the SWAT commander at Pulse said in an interview on Sunday, a week after the shooting.
"The situation is very bad, and we want to save as many people as we can," Mark Canty, the SWAT commander, recalled in a detailed account of what happened at the club.
On at least three occasions during the attack, police opened fire on Mateen. He first came into contact with an off-duty police officer working security who exchanged gunfire with Mateen near an entrance.
Soon after, police stormed into the club, opening fire on Mateen again. Later, after police broke holes in the wall of two bathrooms on the western wall of the club to rescue hostages trapped inside, the officers opened fire on Mateen after they say emerged through one of the holes.
Orlando Police Chief John Mina acknowledged that it was possible people were struck during the crossfire when SWAT officers fired at Mateen during the hostage rescue, saying that this would be part of the investigation into what happened.
The SWAT commander at Pulse said on Sunday he was not sure if any victims may have been struck by officers' gunfire, and the chief medical examiner has said he does not know.
Autopsies of all of 49 people killed at Pulse were finished by Tuesday afternoon, according to the Orange County Medical Examiner's Office, which declined to release those reports.
"This is an active criminal investigation, therefore, the autopsy results and any reports generated will not be released at this time," the office said in a statement.
Florida has broad public records laws, but the state has exemptions for "active criminal investigative information." In an interview with reporters, Joshua Stephany, the chief Orange County medical examiner, said these autopsy reports would not be released due to the federal investigation.
The Orlando Police Department referred questions about the Pulse shooting investigation to the FBI, saying that any information about victims would have to come from the bureau.
The FBI and a spokesman for the US Attorney's Office did not immediately respond to requests for comment about the decision not to release the autopsy reports or say if any of the victims were killed by crossfire.
Stephany said his office did not collect information on whether any victims were killed by police gunfire.
"There would be no way for me to tell if they were shot by police or the shooter," Stephany said. "The same gun can hold different kinds of projectiles. There are too many variables. I am not going to speculate."
Stephany, who said he did not talk to the families about the autopsies, declined to go into specifics discussing the nature of the injuries to victims.
He said that he and and a group of medical examiners recovered projectile fragments from the bodies as well as the club itself for law enforcement in case they need to recreate the scene, but Stephany did not say whether these fragments would be limited to bullets and bullet fragments specifically.
But of the victims, Stephany said: "It's no secret how they died. The injuries were typical of gunfire."
Witnesses at Pulse described seeing many of the victims fall on the floor of the main dance hall, which was riddled with glass and blood after Mateen launched his bloody rampage. Several other people appear to have been killed in one or more bathrooms, where they sought refuge.
It remains unclear if any of the victims could have been saved if police stormed the club sooner. Police have said that after the barrage of gunfire stopped, they treated the situation as a hostage negotiation.
Patience Carter, who Mateen shot in the leg after she fled with into a bathroom stall, said that Mateen shot a number of people, including herself and two friends, one of whom didn't survive, when he rushed into the bathroom early on in the attack.
Mateen ultimately remained holed up with hostages in that bathroom, which police have referred to as the north bathroom, until after police stormed the building.
At a press conference last week, Carter recalled "hours and hours" passing in which the injured and dead around her lay on the floor beneath the stalls in pools of blood, as victims called 911 and loved ones begging for help.
She said that a man lying on the floor told her that her friend Akyra Murray had a pulse at one point, but Murray did not survive. Angel Santiago, another survivor, said that Mateen went into both bathrooms during the standoff, and it is not clear how many people he shot in the two rooms.
Carter also said that after police called for people inside to back away from the wall - before police broke through it at the end of the ordeal - Mateen appeared to shoot at least three people inside the bathroom.
According to Canty, the SWAT commander, once Mateen retreated to the bathroom it did not appear any more shots were fired, except for possibly in the moments when police moved in for the final confrontation with him.
US Attorney General Loretta Lynch said on Sunday that authorities will release "limited transcripts of the calls" between the attacker and the Orlando police negotiators during the standoff, telling CNN that these will show what the gunman said to police officers during the standoff. Lynch also plans to travel to Orlando on Tuesday, the Justice Department said.
In the minutes and hours after the first gunshots, officers from the Orlando Police Department scrambled to take as many people as possible out of harm's way, Canty said in a 45-minute interview on Sunday, providing a detailed account of the SWAT team efforts.
Patrol officers and others moved all those they believed to be living victims out of the patio and dance floor areas, and - while Mateen was holed up in a bathroom on the club's west side - trained SWAT officers took people out of the dressing rooms on the club's north side.
Canty said he was not sure what happened specifically to those who were gravely wounded inside the club and potentially unable to communicate. But he said officers always worked with the victims in mind.
"There's never really a time when we're not trying to save people," Canty said.
Canty said he was sitting on his couch and watching TV when he first got a page activating the SWAT team after 2am on Sunday morning. He said SWAT officers were told initially there was an "active shooter," and then, later, that "he was barricaded with possible hostages inside the nightclub."
"It was so dynamic; it was so fluid," Canty said.
Canty said he got dressed and rushed to the scene, arriving about 2.45am. Before SWAT arrived, Orlando police officers had already exchanged gunfire with Mateen inside the club, Canty said. He said an officer working off duty encountered Mateen about 2am and was the first to do so.
Canty said that, in active shooter situations, even non-SWAT officers are told, "You're immediately to go to the gunfire." He noted the first officer "did engage" the shooter, but Canty said he was unsure why he did not immediately rush after the attacker, and he was also not sure if the encounter happened inside or outside the club.
"I don't know what he heard, what he saw," Canty said. "He has a handgun. The suspect has a rifle. Those are considerations."
After that encounter, more officers were called and another shootout ensued, at which point Mateen retreated into the bathroom with hostages. It is not clear why the police officers who exchanged gunfire with Mateen did not pursue him into the bathroom.
A police officer from Belle Isle, Florida, said an officer from that city south of Orlando was one of four who exchanged gunfire with Mateen before the attacker went into the bathrooms. The Belle Isle officer said he cleared rooms until SWAT arrived and began to evacuate people.
While inside the bathrooms with hostages, Mateen called 911, pledging allegiance to the Islamic State, and also called a television news station and exchanged text messages with his wife, officials said.
During the chaos, SWAT officers rescued some people from dressing rooms on the north side of the club, popping out on an air conditioning unit in one to facilitate the escape. But in the bathrooms on the club's west side, Mateen had taken hostages whose rescue would prove more challenging, Canty said.
Mateen was in the north bathroom, though there were also people trapped in the south bathroom, and an attempt to flee would have forced them to cross Mateen's path, Canty said.
"They only way to get out is to come out the door which is right directly across the hall from where he is," Canty said.
He said as Mateen talked with crisis negotiators, those in command weighed their options and worried what Mateen might do next. "This is someone who is determined. . . they've already killed several people, there's a possibility they may have explosives," Canty said.
When Mateen threatened to strap explosive vests onto hostages, police made their decision to breach knowing the potential consequences, Canty said.
"Once we do the breach," Canty said, "he will know." Canty said the "kind of deciding factor in all of this is we know there's a possibility he'll kill more people."
Canty said the explosives did not blow down the entire wall, so officers then crashed into it with an armored vehicle. That, he said, created a hole between the bathrooms, which was not the spot that police had intended.
He said officers threw distraction bombs in the hole they had created and used the vehicle to break another hole in the wall - this one leading to the south bathroom. Survivors, he said, emerged from that.
Canty said Mateen eventually emerged from the hole between the bathrooms and fired at SWAT officers, who shot and killed him. Not knowing if Mateen might have strapped explosives to himself, officers breached another hole in the north bathroom wall for more survivors to escape, Canty said.
Canty said the department would thoroughly assess its officers' actions to determine if anything could have been done differently, though, for now, he was "very proud" of how all those responded.
"I think we did a good job. Obviously, we would have liked to save more people," Canty said. "That's the worst part of this. I think we did an outstanding job, but unfortunately people still died, but I think that's more on him."
When asked how Mateen was able to kill so many people, Canty said the gunman was "an evil person" who was determined to carry out a massacre.
"If someone is determined to kill a lot of people, they can do it, whether they have an AR-15 or a handgun or whatever they have," Canty said.
Stephany, the medical examiner, said it appeared that few if any of the dead suffered.
"The way we determine suffering is if there is evidence of people moving after an incident," he said. "There was no evidence of that."
The police officers at Pulse, Canty said, "did everything they could to save as many people as they could," and, "they'd do it again. No questions asked."