"No worries," the 47-year-old wrote back. "I've got plenty of firepower."
In another message to a friend, Mazzella said he was waiting for Sander "to make a move on my property so I can legally take him out," according to later court testimony. "[H]e comes near me, he leaves in a body bag," he texted to another friend.
But when violence broke out on Clearsprings Drive on March 25, 2016, it was Mazzella, his wife Stephanie, 43, and his mother, Elaine, 76, who were killed.
Clutching a Mossberg shotgun, Sander entered the Mazzella house and opened fire. "When I shot him, I felt like I got my revenge," Sander told investigators, according to an interview tape obtained by WRAL.
On Monday, Sander was convicted of three counts of first-degree murder. According to WNCN, the case has now entered the sentencing phase, where a jury will decide if the 55-year-old will spend the rest of his life in jail or face the death penalty.
But the proceedings this week have already complicated the picture of the killings. At the heart of the case, surprisingly, was an argument about health care.
On Wednesday, a psychiatrist hired by the defense revealed that two days before murdering his neighbors, a distraught Sander and his wife had gone to a mental health clinic. There, he was told he would have to pay $250 for an assessment. The couple did not have the money, so they left - and Sander went on to murder.
Had Sander had the money, or had the fee been waived, mental health professionals may have realized they were dealing with a man on the verge of violence, Dr. George Corvin testified. "I don't want to be Monday morning quarterback, [but] two days before this he sought treatment and it was not allowed because of financial constraints," Corvin said.
It was at least one of two missed opportunities that could have helped to avoid the suburban carnage.
During the murder trial, the jury heard testimony that the initial cracks in the close relationship between the two men developed when their business ran into money problems and the Mazzella family suspected Sander of embezzling, the News & Observer reported.
Sander also apparently taunted Mazzella that he and his wife had a sexual encounter with Mazzella's wife." PS me and Lori fooled around with your wife," Sander texted his neighbor on Feb. 24, 2016.
The allegation that Sander had molested one of Mazzella's children (he has not been charged in relation to those claims) only put the tension into hyper-drive. Weeks before the shooting, Mazzella showed up in tears on a friend's doorstep, the News & Observer reported.
"He was afraid for his life," the friend told the jury at the trial. "He was just afraid there was going to be a battle."
On Feb. 25, 2016, Mazzella was granted a civil order temporarily banning Sander from contacting the family. The next day, Mazzella's father, Salvatore, filed and was granted a similar restraining order. The News & Observer reported that in an affidavit filed with the court, Mazzella said Sander had made "threatening texts" and "in-person threats."
At the time, the molestation accusation was also beginning to wear away at Sander's psyche, his attorneys claimed in court. Sander himself would later tell investigators the charge could ruin all he had worked toward in his life. The stress may have been compounded by existing medical conditions.
On Wednesday, Corvin, the psychiatrist, told jurors Sander had been committed to mental hospital on two previous occasions after physicians described him as "psychiatrically dangerous," WNCN reported.
Corvin stated Sander "meets diagnostic criteria for bipolar 1 disorder with a history of mood congruent and psychotic features," as well as "elements of paranoid and obsessive compulsive personality disorders."
On March 23, 2016, Sander and his wife went to the local mental health clinic, but could not pay the assessment fee.
"You look at this and say my goodness, this is a very dangerous situation emerging," Corvin testified. "And if . . . I was a psychiatrist there, and he was willing to talk about what he was thinking, he would have been committed again."
The day after Sander failed to get medical help, another decision would similarly set the course for a violent showdown.
On March 24, 2016, Mazzella and his father both appeared before a Wake County district court judge to petition for a one-year restraining order against Sander.
"I want the court to know that I fear for my life, and I fear for my family's life, because of this monster I see in front of my eye," Mazzella's father told the judge, according to the News & Observer.
The petition, however, was rejected. The judge ruled the Mazzellas "failed to prove grounds for issuance of a no-contact order."
The next day, stewing over the molestation allegation and with the alcohol and marijuana he had consumed pushing him toward a blackout, Sander "reached his breaking point," he would later tell investigators.
"I started to scream and bang on the bed," he said. "This isn't fair. I worked my whole life - my family - and then I just went blank . . . I don't know all the details. All I said is my life is over and now I'm going to get even."
Mazzella's father, Salvatore, was inside his son's house when Sander burst in with the Mossberg and opened fire. He escaped and flagged down a driver, who called police.
Sander was taken into custody at his home while his "hysterical" wife and "agitated" three children watched from outside, a first responder testified at the trial, the News & Observer reported. The family feud was apparently still alive in the moments after the killing.
"My father did it," one of Sander's daughters told the first responder. "They deserved it. They tried to kill us and my cat and my dog."
