A Northern California mother is mourning the loss of her son and daughter in separate weekend tragedies, after her son died in the hospital Tuesday morning.

Christina Chavira, a spokeswoman for Enloe Medical Center in Chico, says 20-year-old Billy Carrigan died from injuries suffered in a weekend vehicle accident.

The University of California, Berkeley student had been driving home to the far Northern California town of Chester on Sunday after he learned of his sister's death earlier that day.

Just outside town, he crashed his Toyota Tacoma pickup truck into pine trees along Highway 36. He had been in the hospital in critical condition until he died Tuesday morning.

Carrigan's sister, Jennifer, had been found dead Sunday afternoon by their mother inside the family home in Chester, about 150 miles north of Sacramento. Jennifer Carrigan had been killed along with her date, Steven Furtado of Willows.

Both were 18 and had gone together to the Chester High School prom on Saturday night.

Plumas County sheriff's deputies arrested 18-year-old Reyes Carrillo in the teens' deaths. Patrol Commander Gerry Hendrick says Carrillo had previously dated Jennifer Carrigan.

Carrillo is set for a court appearance Tuesday afternoon.