TUSTIN – A naked man was struck and killed by a pickup Friday morning after he jumped out of an ambulance and into freeway lanes, the California Highway Patrol said.

The fatal accident occurred after a man sheriff’s deputies had picked up for a mental evaluation escaped from an ambulance on the northbound I-5 just south of the 55, authorities said.

The man was originally picked up by deputies responding to reports of a possibly suicidal 21-year-old at a home in the 23000 block of Eagle Ridge Drive in Mission Viejo about 8 p.m. Thursday, said Jim Amormino, an Orange County Sheriff’s Department spokesman.

The man wasn’t home when deputies arrived, Amormino said, but returned about 10 minutes later and voluntarily agreed to go with deputies for a mental evaluation at Mission Hospital.

Mission Hospital officials treated the man and decided that he needed to be taken to a facility in Los Angeles, Amormino added.

The man reportedly began to act erratically on the ambulance ride to Los Angeles about 7:45 a.m. Friday.

The driver of the ambulance was forced to stop along the center divider of the I-5 freeway, said John Patterson, a CHP officer.

“He was getting out of his restraints, so they went to readjust the restraints, and that is when he broke free,” Amormino said.

Patterson said the man jumped over a concrete center divider, ran across the southbound I-5 lanes, and then ran into the southbound 55 connector to the southbound I-5.

At that point, authorities say, an off-duty sheriff’s deputy grabbed the man and attempted to calm him down.

“(The deputy) just happened to be driving on the freeway coming home from work and saw the guy running around,” Amormino said.

The man broke free from the deputy and jumped in front of a pickup, which struck and killed him, Patterson said.

The man, who authorities later identified as Brett Weiner, 21, of Mission Viejo was pronounced dead at the scene.

Register photographer Bruce Chambers contributed to the report.

Contact the writer: amolina@ocregister.com or 714-704-3795