The suspect who shot a UPS driver in broad daylight in an ambush killing as the victim was on his delivery route in Southern California was a childhood friend of his and a coworker, prosecutors said. 

Rhean Jalipa Fontanoza, 46, allegedly shot 50-year-old Expedito De Leon 10 times "in a matter of seconds as he sat seat belted in his delivery truck" on May 16, the Orange County District Attorney's Office said Tuesday. 

"He still had his UPS scanner in his hand and his seatbelt buckled when Fontanoza drove up next to De Leon’s delivery truck and shot [at] him 14 times in 19 seconds," the DA's office said. 

Authorities said Fontanoza fired 14 shots and 10 hit De Leon. 

USPS MAIL CARRIER SHOT AND KILLED ON THE JOB, POLICE OFFERING $250K REWARD FOR INFO

Rhean Jalipa Fontanoza, bottom and Expedito De Leon, top

Rhean Jalipa Fontanoza (bottom), 46, allegedly shot and killed his coworker and childhood friend, Expedito De Leon (top), 50, as the victim was inside a UPS truck last week.  (KTTV; Irvine Police Department)

Fontanoza, a UPS employee who was on disability leave, is charged with a special circumstances allegation of shooting from a vehicle and murder by lying in wait.

He allegedly went to great lengths to track down De Leon's delivery route on the day of the killing. He allegedly stopped another UPS driver at around 12:30 that day and asked if it was the same delivery route used by De Leon.

The driver said De Leon was on a different route, prompting Fontanoza to go to the UPS substation in Aliso Viejo, where he was allegedly seen accessing a computer that shows driver routes and taking a picture with his phone. 

"Just before 3 p.m., Fontanoza is accused of tracking De Leon down on his route and driving past him a new vehicle which De Leon wouldn’t recognize. De Leon then left his truck to make a delivery and returned to his truck, and buckled his seatbelt," prosecutors said. 

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UPS truck at crime scene

A UPS driver was shot and killed in what police believe was a targeted attack on Thursday in Irvine, California. (FOX 11 LA livestream/Screenshot)

After the murder, Fontanoza fled the scene but was found by authorities in his vehicle later that afternoon, prosecutors said. He refused to get out of the car until tear gas and a police K-9 were deployed, authorities said. 

Orange County District Attorney Todd Spitzer said De Leon "was just going about his day, doing his job with no idea his longtime friend was stalking him with every intent to kill him." 

"The depravity involved to plot and carry out a plan to execute someone you shared a lifetime of memories is not something anyone of us can wrap our heads around," he added. "No life should have to end like this and it is a tragedy that should have never happened."

Silver pickup truck barricaded by police vehicles

The shooter accused of killing a UPS driver on Thursday in Irvine, California, barricaded himself inside his truck before police forced him out and arrested him. (FOX 11 LA livestream/Screenshot)

At the time of the killing, Fontanoza was scheduled to return to work on June 1 from disability leave.

Investigators have not determined a motive for the attack. Fontanoza is being held in the Orange County Jail with no bail. He is eligible for the death penalty, prosecutors said. 

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In a statement to Fox News Digital, UPS said it was "shocked and saddened by the latest developments in Irvine, CA. These are highly unusual circumstances and do not represent the culture of our company and the camaraderie among our employees around the world."

"Our focus now is on supporting our people and their loved ones during this extremely difficult time. Since the investigation is ongoing, we defer any additional questions to the investigating authorities," the company said.