CHICAGO (CBS) — A man is set to be sentenced Monday in the 2008 murder of a pizzeria owner whom the man thought was part of a rival gang.

As WBBM Newsradio 780’s Michele Fiore reports, prosecutors say Contreras was out for revenge the night of Aug. 10, 2008. He was recovering from a gunshot wound to the shoulder, delivered by a member of a rival gang.

That was when he spotted Jason Mueller, 29, who was trying to hail a cab at Grand and Wolcott avenues in the Ukrainian Village neighborhood.

Mueller had gone to a club after leaving work, and had then driven a friend home in the friend’s car, prosecutors said at the time. But he was not part of the gang Contreras was out against, or any other gang, for that matter.

Mueller was, in fact, the owner of Nonna’s Italian Pizzeria, located at 1543 N. Sedgwick St.

Jason Mueller

Pizzeria owner Jason Mueller was gunned down on Aug. 10, 2008. (Credit: CBS)

“Jason had no enemies. Everyone who knew Jason liked Jason. We don’t see any reason why anyone would have done this,” a co-worker, Heather Oestmann Schwartz, said at the time of the murder.

LISTEN: Newsradio 780’s Michele Fiore reports

Mueller was shot once in the face, chest and buttocks.

It was a co-defendant, Anthony Collazo, who was charged with firing the shots that killed Mueller. But Collazo, 19, was acquitted of charges.

Contreras will be sentenced later Monday.

The Sun-Times Media Wire contributed to this report.