CHICAGO (CBS) — An off-duty Chicago Police officer shot at two robbers, fatally wounded one, during a sale of a computer.

Hazel Crest police responded around 10 p.m. Tuesday night to a call of shots fired and a robbery on Birchwood Drive.

Upon arrival, officers found a man with his hands in the air, who identified himself as a Chicago Police officer, police said in a news release. The Chicago police officer was off-duty and said his weapon was on the hood of his car, which Hazel Crest officers secured.

The officers also found a second male lying face down between two nearby houses. The man had a gun in his hand and a Chicago Police badge next to him on the ground, police said.

After checking the man’s vitals, officers called Hazel Crest paramedics, who were unable to revive the man.

Upon a search of the man’s pockets for identification, officers found a key fob for an automobile, later verified to belong to the off-duty Chicago Police officer.

Hazel Crest Police believe the off-duty Chicago officer met with subjects who were supposed to sell him a computer. The arrangements of the met-up were initiated through an online sales network. Upon arrival to Hazel Crest, the off-duty officer exited his vehicle and approached two subjects who said they had a computer for sale.

Then one of the offenders drew a handgun, held the off-duty officer at gunpoint and removed his personal belongings from his pocket. The offenders then discovered the officer’s badge and firearm. They took his badge but before they could disarm him, the off-duty officer was able to fire at both offenders.

One of the suspects, identified as 17-year-old Aaron Brandon, fell between two houses nearby, according to police and the Cook County medical examiner’s office. The other fled the scene.

Brandon, a Homewood resident, was pronounced dead South Suburban Hospital in Hazel Crest at 10:42 p.m., according to the medical examiner’s office. An autopsy Thursday found he died of multiple gunshot wounds, and his death was ruled a homicide.

Hazel Crest detectives are investigating the armed robbery, while the Illinois State Police Public Integrity Unit is investigating the officer’s use of force.