By Kerri Corrado

PHILADELPHIA (CBS) — Family and friends are remembering Thomas Siderio on what would have been his 13th birthday. He is the boy who was shot and killed by police in South Philadelphia earlier this month.

The family is still grieving and wants justice as the investigation continues.

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Family and friends remembered the life of TJ Siderio on what would have been his 13th birthday.

“I want my grandson to rest in peace,” said Maryhelen Siderio, TJ’s grandmother.

On March 1, Siderio was shot and killed by police after investigators say he fired at an unmarked police cruiser in South Philly and ran.

TJ’s family hired attorneys and is challenging the police account of his death. His grandfather had a strong, emotional message to the officer who fired the fatal shot.

“This message goes out to the Philadelphia cop that killed my 12-year-old grandson: I want to know why you shot him in the back,” Thomas Lawler III said.

Philadelphia Police Commissioner Danielle Outlaw says as Siderio ran, an officer fired his gun, striking him in the back and killing him. That officer was suspended with the intent to dismiss after violating the department’s use of force directive. Outlaw did not specify the violation.

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While the investigation continues, TJ’s family celebrated his life with stuffed animals, candles, cake, homemade signs and balloons.

“It’s only been 27 days and we are still grieving,” Siderio said.

As TJ’s family grieves, they are remembering what they loved about him the most.

“TJ was a great, wonderful kid. He would help anybody out. He loved his family and friends,” Lawler said.

As the family seeks justice, they too are fighting to end the gun violence epidemic in the city.

“The police department and everyone else has to get together and stop these young kids with the guns,” Siderio said.

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The investigation is far from over. In the meantime, TJ’s family is working to keep his memory alive.