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Gregory Charles Davis, 54, was ordered held on $500,000 bail.

Deputy District Attorney Christopher Moon told Judge David Szumowski that Davis and the stabbing victim were both riding on the trolley about 12:30 p.m. Monday when the defendant -- seemingly unprovoked -- slashed the victim in the throat.

"At one point without any provocation the defendant stabbed the victim in the throat. The stabbing caused a four-inch laceration to the victim's neck. It lacerated the victim's trachea and also his thyroid gland," said Moon.

Davis and the victim apparently knew each other, the prosecutor said.

Once off the trolley, Davis allegedly confronted a 75-year-old man near Perry's Cafe, demanding the keys to his car, Moon said.

"He demanded car keys the man had in his hand. The defendant then punched the victim in the chest before being given the keys, thereafter the defendant sped off in the stolen car," Moon said.

Davis drove off recklessly, causing two hit-and-run crashes, the prosecutor said.

Shortly before 3 p.m., a television news cameraman driving through Clairemont Mesa spotted the stolen Buick parked and abandoned alongside the southbound lanes of Interstate 805, near Mesa College Drive, police said.

Officers with a service dog searched a brushy open area into which the carjacker apparently had fled after pulling over on the freeway, according to police. About 4 p.m., police took the suspect into custody off the 7800 block of Mission Center Road.

Davis will be back in court Oct. 7 for a readiness conference and Oct. 12 for a preliminary hearing.

He faces 15 years in prison if convicted of attempted murder, carjacking, elder abuse and two misdemeanor counts of hit-and-run. Moon said.