A UPS driver was found shot to death in his truck Thursday afternoon, and a co-worker with the delivery company has been charged with killing him.

Irvine, California, police were called to the scene by multiple reports of shots fired at about 3 p.m., KCAL reported. Officers found Expedito Cuesta De Leon, 50, slumped over in the driver’s seat and pulled him out of the truck to begin life-saving efforts, but he died from his injuries.

About three hours later, police arrested Rhean Fontanoza, 46, saying the two men were “acquaintances” who both lived in Aliso Viejo and worked for UPS.

A motive for the shooting remains unclear, however. Investigators say nothing was taken from the truck, and Fontanoza may have targeted the victim.

Police said they tracked Fontanoza after seeing surveillance video showing a Honda Ridgeline pick up truck briefly pull alongside the UPS truck before driving away.

Orange County Sheriff’s deputies later spotted a vehicle matching the description about an hour later on Santiago Canyon Road. Irvine officers arrived on the scene and confirmed it was the same truck seen in the surveillance footage.

“Our hearts are heavy with the news of the loss of one of our drivers in Irvine, CA, and we are assisting authorities to understand what happened,” UPS said in a statement.

Armored police vehicles boxed the suspect truck in, and Irvine SWAT officers took Fontanoza into custody, KABC reported.

Anyone with information should contact Detective Craig Voors at 949-724-7131 or email him at cvoors@cityofirvine.org.

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[Featured image: Expedito Cuesta De Leon/Facebook and Rhean Fontanoza/Irvine Police Department]