A Wentworth Area detective was shot in the lower back about 12:50 a.m. near West 50th Street and South Peoria Avenue, according to police News Affairs Officer Hector Alfaro.
The Chicago Police detective was taken to Stroger Hospital, where he underwent surgery and was in serious condition late Monday, authorities said.
As the officer approached a man standing on the street, the man took off running.
As the detective chased the man, he heard a gunshot, police said.
The detective had been shot in the lower back, just above his belt, said police Sgt. Eugene Mullins.
For the "know-it-alls" who say he wasn't wearing his vest.
A suspect had been arrested in connection with another police-involved shooting, according to a Harrison Area detective.
The officer fired shots at the suspect, who was armed, in the Near West Side's Wood District about 1 a.m. near West Carroll and North Hoyne avenues, according to the detective.