Investigators say a 47-year-old man was riding a mountain bike when he was hit near Ridge Route Drive and Serrano Road around 10 p.m. on Tuesday.
The victim was transported to the hospital with severe head trauma. He succumbed to his injuries early Wednesday morning.
Detectives looked for clues that might lead them to the driver of a white minivan who struck and killed a man riding a bicycle just after 10 p.m. Tuesday near El Toro High School.
"We believe that he was on the sidewalk, came down the handicap area into the crosswalk, where he was struck by the white minivan," said Orange County Sheriff's Spokesman Jim Amormino.
The 47-year-old cyclist was identified by his family as Randy Isaacs.
"He was going to another house down the street three blocks away from us. He had put his daughter to bed, kissed her goodnight and said 'Jesus loves you and so do I.' And the next thing we know, we get a call from the hospital that he's dead," said Ute Ford, the victim's mother.
Why the driver of the vehicle hit the man is not clear. Why he or she didn't stop is also unknown.
"There may be a logical explanation to the accident. We're asking the driver to come forward. Tell your side and we'll figure out exactly what happened," said Amormino.
Authorities suspect the vehicle, last seen heading northbound on Serrano Rd., has front-end damage from the crash.
The driver may also live in the area or have been visiting someone since the intersection is located in a residential area nearly three miles from the freeway.
"We're asking the public to please help us, please please help us find this person that killed my son. He has three children that aren't going to have a Christmas with daddy," said Ute Ford.
Authorities are looking for a white van with possible front-end damage. Anyone with information is asked to call the Orange County Sheriff's Department tip line at (866) 847-6273 or Orange County Crime Stoppers at (855) TIP-OCCS.