While the family of Thomas “TJ” Siderio prepares to bury the 12-year-old boy shot and killed by Philadelphia police, investigators are examining whether he had tossed a gun moments before a fatal bullet struck him in the back.

Two plainclothes officers chased TJ on Tuesday night after they heard gunfire and a rear window shattered in their unmarked car near 18th and Barbara Streets in South Philadelphia.

They fired toward TJ, who they said was holding a handgun and fled east on Barbara Street.

» READ MORE: What we know — and don’t — after Philadelphia police fatally shot 12-year-old Thomas Siderio

New details reveal that the officers fired four shots in total, according to police sources.

During the first two blasts, TJ was holding a gun. But the last two shots — one of which was fatal — are “concerning,” the sources said, because TJ may have tossed his weapon before he was hit.

Investigators are combing through video footage that captured the shooting and its aftermath. Some footage was obtained from neighbors who had video-equipped doorbells. The officers were not wearing body-worn cameras.

» READ MORE: Update: The Philly officer who fatally shot a 12-year-old boy will be fired, Commissioner Danielle Outlaw said

Four officers were sitting in an unmarked car when the episode began around 7:20 p.m. They were Edsaul Mendoza, Kwaku Sarpong, Robert Cucinelli, and Alexander Camacho, according to police records obtained by The Inquirer. They were staking out the area because a 17-year-old boy and 20-year-old man had been seen on social media brandishing weapons, police sources said.

The officers approached TJ and a 17-year-old, who were on bicycles, police said, because they believed one of them had a handgun. They turned on their flashing lights, then heard gunfire. Camacho was injured in both eyes by shards of glass, police records show.

Two officers got out of the car, took chase and fired at TJ.

Investigators recovered a 9mm semiautomatic handgun that they said TJ was carrying. It was equipped with a laser and loaded with one round in the chamber and five rounds in the magazine, police said.

Investigators found five shell casings at the scene.

The two officers who fired their guns that night are not identified in the police records. The fatal bullet struck TJ in the upper back and exited through his chest, police said.

According to Police Department policy, an officer would not be justified in using deadly force solely if a suspect resisted arrest or attempted to escape. Other factors are supposed to be taken into consideration, such as whether a suspect was armed, or posed an immediate threat to an officer. Officers should not shoot at a fleeing suspect “who presents no immediate threat of death or serious bodily injury,” the policy states.

Philadelphia police investigators and the District Attorney’s Office Special Investigations Unit are probing the shooting. A spokesperson for the District Attorney’s Office declined to comment, citing the investigation.

City Councilmember Kendra Brooks on Friday called for an independent investigation into TJ’s death. “His community, and all of our communities, deserve answers,” she wrote in a statement. “We need a full, independent investigation into the circumstances that led to TJ’s death, and real accountability for the responsible officers.”

”... Under no circumstances is it justified to shoot and kill a 12-year-old fleeing the scene of a crime in the back. Such a devastating incident points to a serious failure of our city’s approach to community safety.

TJ, who was in seventh grade at George W. Sharswood Elementary School, was taken to Penn Presbyterian Medical Center after the shooting and pronounced dead minutes later. He became the youngest person to have been fatally shot by a Philadelphia police officer in decades.

Kim Tomasetti, the mother of the 17-year-old, who was not charged, said he told her the officers did not turn on their emergency lights or identify themselves as police before any shots were fired. The boys, she said, were afraid that someone in the car was about to attack them and didn’t know they were officers.

Tomasetti said she believes the shooting could have been avoided if officers had identified themselves sooner.

Three of the officers could not be reached for comment. Mendoza declined to comment, as did the union that represents Philadelphia police officers.

Citing departmental policy, a Police Department spokesperson said that officials could not confirm the names of the officers. With concerns for the officers’ safety, officials are awaiting a “threat assessment,” before they release names.

In the last six months, there were 652 crimes reported in the South Philly area where TJ was shot and killed, according to city police statistics. The area — bounded by Snyder Avenue south to I-76, and Broad Street west to 25th Street — saw two homicides, 36 robberies, and 23 aggravated assaults in that time period.

TJ’s father, Thomas Siderio Sr., initiated a lawsuit against the four officers Friday by filing a writ of summons, which does not as yet include a complaint. Siderio, 28, is “devastated” about the death of his son, said J. Conor Corcoran, a civil rights attorney representing him.

“The family is just wiped out by this,” Corcoran said. “And it speaks to how much reform and oversight is needed in the Police Department and how now it is devastatingly bereft.”

Siderio initiated the lawsuit from his state prison cell in a facility near Hazleton, where he is serving time for firearms convictions. He has been incarcerated there for the last three years and has at least two more years to go.

He has a criminal history that includes a 2017 arrest for murder in a case in which he was found not guilty. But he was convicted of gun charges in the case, leading to his current imprisonment.

He has sued the city before, using the same lawyer. In 2015, Siderio filed a federal suit naming four officers — none of whom was involved in his son’s death — with beating him and putting him in a chokehold in front of a South Philadelphia corner store. The suit was settled a year later.

It could not be immediately determined if the city paid money to resolve the suit. Siderio later pleaded guilty to resisting arrest in connection with the incident. Earlier, he was given other shorter jail terms for an assault conviction and for using bolt cutters to steal a Suzuki motorcycle.

TJ’s mother, Desirae Marie Frame, could not be reached for comment.

A memorial for TJ, with candles and messages, continued to grow Friday outside Barry Playground near the shooting. A purple candle and “we love and miss you” was written in red on his wooden desk at school.

A viewing for TJ will be held Wednesday between 6:30 and 9 p.m. and again on Thursday from 10 to 11 a.m. at the Lighthouse Baptist Church, 2400 S. Broad St. Services will begin at 11 a.m. Burial follows at Fernwood Cemetery.

Family friend JoAnne Moore launched a GoFundMe Thursday night to pay for funeral expenses.

As of Friday night, $3,000 had been raised. The goal is $12,000.

“The death of a child is not only devastating but it is a tragedy no matter what the situation,” Moore wrote. “These grandparents must now say goodbye to their only grandchild, the grandchild they could not save. Please help alleviate some of the financial expenses that his funeral will cost. Every child deserves a beautiful and peaceful forever home.”

Online, memorials and other remembrances have poured in from friends, family, and neighbors across South Philadelphia, where many described the boy as a neighborhood fixture.

”Missing u like crazy” reads one online tribute, “Funniest kid ever u put a smile on everyone’s face.” Using the hashtag “LLTJ” — or “Long live T.J.” — many expressed shock over the child’s sudden and violent end.

”No matter the circumstances he was just a boy,” wrote one relative in another social media post. “There is a family and community of children mourning and trying to understand the death of another child.”

Staff writers Rodrigo Torrejon and Max Marin contributed to this article.