CHICAGO — A 26-year-old gunman was shot and killed by a Walgreens security guard following an altercation in South Shore Thursday evening.

According to the Chicago Police Department, officers responded to a shooting near the intersection of 71st Street and Jeffery in the South Shore neighborhood at 2:50 p.m. on Thursday.

Witnesses told WGN that the incident started with two men on the sidewalk, one of the men was selling some sort of merchandise, before a fight broke out. The 26-year-old man pulled out a gun and shot the the 22-year-old. A security guard from the Walgreens nearby came out and fired shots at the 26-year-old gunman.

The 22-year-old was transported to University of Chicago Medical Center in critical condition.

The 26-year-old, identified as Kyle Eastes, was also transported to University of Chicago Medical Center where he was later pronounced dead.

The Walgreen security guard reportedly is a part-time police officer at Cook County Hospital, according to the Chicago Police Department.

No further information has been reported at this time.

Stay with WGN-TV as this story develops.