"We want this investigated as a hate crime. It was clearly racially motivated," Liell said. "We will continue our quest every day until some justice is served."
Booker said he's pleased the FBI got involved.
"I'm sad that this happened, honestly," Booker said. "I just wanted to have a good time with some friends."
Liell also complained that law enforcement officers with the Indiana Department of Natural Resources "did not move rapidly enough" in response to reports of the attack. She said their failure to make arrests at the scene warrants further investigation from other law enforcement agencies.
Bloomington Mayor John Hamilton said at the news conference that police continue to search for two people accused of knocking a woman unconscious and dragging a man with their car at a protest over the assault on Booker.
Police Captain Ryan Pedigo told AP that the confrontation happened near the Monroe County courthouse in Bloomington yesterday.
A male passenger got out of a red Toyota car and went to move an electric scooter that had been left in the road near the protest site, Pedigo said. A 29-year-old woman approached the car and placed her hands on the hood, he said.
The driver accelerated into the woman, launching her onto the hood. A 35-year-old man then grabbed the driver's side of the car and held on as the vehicle continued to accelerate. Both were eventually flung to the ground and the car fled the scene, Pedigo said.
The woman was knocked unconscious and suffered a cut to her head, while the man scraped his arm. She was transported by ambulance to a hospital but her injuries are not believed to be life-threatening, Pedigo said. Authorities have not released the identities of the injured nor said if they were participating in the protest.
The red Toyota has not been located and investigators are still trying to determine the identities and location of the male passenger and female driver, police said in a news release.
Several protesters provided police with cellphone footage, Pedigo said.
"The event last evening is being actively and aggressively investigated right now," Hamilton said. "We are taking whatever steps it takes to bring justice to that event."
The protesters had gathered in Bloomington, about 80km southwest of Indianapolis, to demand arrests in the assault on Booker.
Meanwhile, at least seven men forcibly restrained a teenager who had a heart attack and died two days later.
The staffers at a youth facility in Michigan held down the boy's arms and legs and sat on him as he screamed that he couldn't breathe, a lawyer representing the boy's estate said today.
Surveillance video footage from the Lakeside Academy in Kalamazoo shows 16-year-old Cornelius Fredericks being pushed to the floor and held down by staff members because he threw a sandwich in the cafeteria. About a dozen teenagers can be seen sitting in the cafeteria at the time.
The video was released by Detroit-area lawyer Geoffrey Fieger, who represents Fredericks' estate. A civil lawsuit filed by the estate in June says the boy screamed "I can't breathe" on April 29 as he was restrained for what appeared to be about 12 minutes on video released by the state.
The teenager went into cardiac arrest, was hospitalised and died two days later, authorities said. The death was ruled a homicide and the doctor who performed the autopsy said Fredericks died of asphyxia.
Two male staffers and a female nurse were fired and have been charged with involuntary manslaughter and second-degree child abuse in Fredericks' death.
Fieger said he is urging authorities to recommend charging others.
"As you can see in the video, far more than two people are involved in suffocating him," Fieger said.
Fredericks had been a ward of the state for several years, following his mother's death when his father was incarcerated.
- AP
