CHICAGO (CBS) -- Four people were wounded in a shooting in a residence in the South Side's Brainerd neighborhood Monday evening.

Police said at 7:03 p.m., the victims had gotten into a quarrel in a second-floor residence in the 9300 block of South Racine Avenue. A 16-year-old boy then took out a gun and fired shots – striking three people.

One 15-year-old boy was shot in the right shoulder and was taken to the University of Chicago's Comer Children's Hospital in fair condition. Another 15-year-old boy was shot in the abdomen and left arm and was taken to the same hospital in critical condition.

A 21-year-old man was shot in the right shoulder and buttocks, and suffered a graze wound to the forehead. He was taken to Advocate Christ Medical Center in Oak Lawn in critical condition.

The 16-year-old shooter also suffered gunshot wounds to the right hand and abdomen, and was taken to the U of C's Comer in fair condition. Police did not specify whether he was shot by someone else – and who, if so – or whether the wound was self-inflicted.

Area 2 detectives are investigating the circumstances surrounding the incident, police said. Further details were not immediately available.