CHICAGO — A 15-year-old girl who had performed at President Obama’s inauguration festivities is the latest face on the ever-increasing homicide toll in the president’s hometown, killed in a Chicago park as she talked with friends by a gunman who apparently was not aiming at her.

Chicago police said Hadiya Pendleton was in a park about a mile from Obama’s home in a South Side neighborhood Tuesday afternoon when a man opened fire on the group. Hadiya was shot in the back as she tried to escape.