An East Chicago teen, 16, is facing charges for gunning down a 17-year-old.

Afterward, crying, the alleged shooter told his relative: “I made a big mistake.”

The boy was charged Saturday with murder, attempted murder and a misdemeanor. He also faces two gun enhancements, which would add 5-20 more years to a prison term, if convicted.

The Post-Tribune is not naming him because he is a minor. An initial hearing was scheduled Monday afternoon.

Police responded at 11:16 a.m. March 14 to the Lakeside Gardens Apartments in East Chicago after the city’s shotspotter system activated.

Justin Charleston, 17, of East Chicago appeared shot several times in the torso, Det. James Nielsen of the Lake County Prosecutor’s Homicide Task Force wrote in charging documents.

Investigators found several 9-mm casings in a nearby parking lot.

Police learned the shooter and victim had “past altercations.”

Witnesses heard 5-6 shots. The shooter wore a ski mask, blue coat and black pants, according to security camera footage.

Investigators wrote the shooter was walking in front of Charleston when he turned around and opened fire. Police pulled his school photo from the city of East Chicago for a lineup.

A witness identified the shooter at the police station before they tried to take it back.

A lawyer called an investigator saying the teen would turn himself in. The teen declined to speak with police.

His relative said he heard the shots and rushed to check Charleston’s pulse and called 911. He called the teen, according to court documents. The boy claimed he was at another relative’s home.

“I made a big mistake,” the boy said through tears without elaborating.

mcolias@post-trib.com