CHICAGO (CBS) — A jury returned a guilty verdict against a man who killed a Chicago police evidence technician and a former housing authority cop in 2010, as the tech investigated a car burglary on the Southeast Side.

Timothy Herring, 24, was accused with killing Chicago Police Officer Michael Flisk and former Chicago Housing Authority police officer Stephen Peters.

Flisk was dusting for prints after Peters’ custom Ford Mustang had been stripped for parts on Nov. 26, 2010. Prosecutors said, when Herring found Flisk found a print, he returned to the scene of the crime in the 8100 block of South Burnham Avenue, and killed Flisk and Peters.

The courtroom was packed with police officers and the victims’ relatives when the jury announced its guilty verdict on Wednesday.

Peters’ mother testified she was home at the time. Peters had told her someone had broken into her garage and stole parts from his prized Mustang, and as he was out in the alley waiting for police, she heard two gunshots.

Prosecutors played a recording of Laura Peters’ 911 call when she took the stand, and jurors heard her sobbing, and pleading for help.

“Mrs. Peters is an extremely strong woman; took the stand, and if you were there to hear the 911 call, it’s chilling,” Cook County State’s Attorney Anita Alvarez said after the verdict. “Sees her son laying there on the ground, and we actually hear the second shot on that 911 tape. It’s really chilling testimony.”

Alvarez also said Flisk’s family “has been tremendous, wonderful, and again my heart goes out to both families.”

Jurors began deliberations in the case Tuesday afternoon, and returned their verdict Wednesday morning.

Herring faces a mandatory life sentence for his conviction.