PHILADELPHIA (CBS) -- Philadelphia police promise a fair and thorough investigation after a 12-year boy with a stolen gun on him was shot in the back and killed by a plainclothes officer.
Eyewitness News talked with the mother of a 17-year-old boy who was with Thomas Siderio when he was killed.
A memorial is growing by 18th and Barbara Streets in South Philly. It's where a 17-year-old boy saw his 12-year-old friend get gunned down by police Tuesday night.
We spoke to the 17-year-old's mother. She didn't want to identify herself or her son but had this to say about 12-year-old Siderio.
"He had no chance in life and now, he's gone before he could even get a chance in life," the mother of the 17-year-old boy said.
Authorities are working to find out if the shooting of the 12-year-old was justified.
According to police, plainclothes officers in an unmarked vehicle spotted Siderio with a gun on him, along with the 17-year-old.
Officers activated their vehicle's police lights, but officials say someone then fired at the vehicle.
The boys then ran from the scene and Siderio was still holding a gun. Police say one of the plainclothes officers then drew his weapon and fired, striking Siderio's back, killing him.
"That will be a very fact-specific investigation," Center City-based attorney Jordan Strokovsky said.
Strokovsky is not associated with the case but says as authorities figure out if the deadly shooting of the armed 12-year-old was justified, the investigation will likely consider this.
"Whether at the time of the shooting the child was an active threat," he said.
We're also learning more about Siderio's upbringing.
At age 11, he was reported missing to police missing for about four days. A friend of his family says Siderio has lacked having a father figure in his life.
In a tweet, Philadelphia Police Commissioner Danielle Outlaw said of the 12-year-old, "We as a society have failed him."
Siderio was a seventh-grade student at Sharswood Elementary School, according to a School District of Philadelphia spokesperson.
"We do consider our schools to be safe havens for our young people and places where they can go and really have another family. And we really feel he was one of those children who looked at the Sharswoood community as his family," school district spokesperson Monica Lewis said.
The Philadelphia School District wouldn't elaborate.
Police are still investigating.
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