An argument over $100 allegedly led one mechanic to kill another with a pickup truck Monday afternoon in the parking lot of a West Chatham auto parts store.

Keith Watley, 29, told detectives that he slammed the pickup into 22-year-old Carlos Posadas when he “kind of snapped” after the two men argued and fought over the payment, which¬†Watley owed Posadas for a job they did together, according to Cook County prosecutors.

Watley, of Indiana, faces a count of first-degree murder and was ordered held without bail during a hearing Thursday at the Leighton Criminal Court Building.

Keith Watley | Chicago Police

On Monday, the two men had gotten into an argument over the money that turned physical while they were working on separate vehicles in the Auto Zone parking lot at 208 W. 87th St., prosecutors said in court.

About 3 p.m., Watley got into a Ford pickup truck he was working on at the other end of the lot and drove it to where Posadas was working on a Honda Accord, prosecutors said.

Watley pointed the pickup at Posadas, whose back was turned as he worked, and sped toward him, slamming into Posadas and pinning him between the two vehicles, prosecutors said. After striking Posadas, Watley allegedly drove the pickup over him, causing additional injuries.

Posadas, who lived in West Englewood, was pronounced dead at the scene. His death was ruled a homicide following an autopsy Tuesday.

Watley was taken into custody shortly after the crash when witnesses followed him to an O’Reilly Auto Parts store at 8640 S. Lafayette and called police, prosecutors said.

A public defender for Watley said he lives with his wife and children, served in the National Guard and volunteers with his church and Boys and Girls Clubs of America.

Judge Mary Marubio ordered Watley held without bail.

About a dozen family members and friends of Watley attended the hearing, with some crying after they left the court room. All declined to comment.