CHICAGO — Authorities say a Chicago teenager killed himself after being chased by police, but his family thinks the officers shot him and they’re calling for an independent investigation.

The Chicago Tribune reports that police say 15-year-old Steve Rosenthal fled Friday when officers who allegedly saw him holding a handgun tried to question him. They say shortly after that he fatally shot himself on the back stairwell of his West Side home.

The teen’s family says based on witness accounts they believe the officers shot him.

The family’s attorney, Andrew Stroth, said Sunday that the officers killed Rosenthal “without cause or provocation” within moments of rushing up the stairwell. He says the family demands a “full, independent and transparent” investigation.

More than 120 people gathered Sunday to protest the teen’s death.