Police officers look at a car in which a man was found shot the head late Sunday night in the South Side's Avalon Park neighborhood.

Police officers look at a car in which a man was found shot the head late Sunday night in the South Side's Avalon Park neighborhood. (Adam Sege, Chicago Tribune / September 16, 2013)

UPDATE: Brandon Williams, 31, died early Tuesday morning at John H. Stroger, Jr. Hospital of Cook County.

A 31-year-old man was shot and critically injured Sunday night as he sat in a car in the South Side's Avalon Park neighborhood, police said.

About 11:05 p.m., a single gunshot rang out in the 8000 block of South Woodlawn Avenue, police said, citing witness accounts. When officers arrived, they spotted a car facing southbound that had crashed into a car parked at the curb.

A man in the driver's seat was bleeding from a gunshot wound to the head. He was taken in "very critical" condition to John H. Stroger, Jr. Hospital of Cook County, police said.

Police believe two male assailants ran northbound from the scene after the shooting.

Early Monday morning, the car remained southbound on Woodlawn with its driver's side door ajar, window rolled down.

Small bags of cannabis were found at the scene, police said, while cautioning they had not determined a motive for the shooting.

asege@tribune.com | Twitter: @AdamSege