An Illinois Tollway worker was struck and killed by a semi truck Monday afternoon on the Tri-State Tollway near south suburban Alsip.

At 12:23 p.m., 48-year-old David M. Schwarz was struck by a truck pulling a trailer while picking up debris along the right shoulder on southbound I-294 near 127th Street, according to the Illinois Tollway and the Cook County medical examiner’s office. The semi driver drove off after sideswiping the Schwarz and his vehicle.

Schwarz, who lived in south suburban Monee, was pronounced dead at 12:43 p.m., the medical examiner’s office said. An autopsy Tuesday found he died of multiple injuries after being struck by at least one vehicle and his death was ruled an accident.

Schwarz served as an equipment operator laborer since beginning his career at the tollway in March 1992, according to the tollway’s statement. He was married and a father of two children.

“David worked on the front line of our 292-mile roadway system, performing duties that included removing snow, maintaining safe roadway conditions and, most vitally, assisting drivers who were stranded or needed help,” according to the tollway’s statement. “He was carrying out his duties when he tragically lost his life.”

“We offer our deepest condolences and our full support to David’s family, loved ones and friends for their heartbreaking loss.”

The crash remains under investigation.