CHESTER -- A Northern California mother is dealing with a double tragedy after her daughter was killed during a weekend prom date and her son was severely injured in a car crash.

Jennifer Carrigan and Steven Furtado were found dead Sunday by Carrigan's mother at a house in Chester, about 150 miles north of Sacramento. Both were 18.

When told of his sister's death, 20-year-old Billy Carrigan headed home from Berkeley. Shortly before 7 p.m. Sunday, just before he reached Chester, Billy Carrigan crashed his Toyota Tacoma pickup truck into a stand of pine trees along Highway 36.

A spokeswoman at Enloe Medical Center in Chico said he was in critical condition Monday.

It was not immediately clear how Jennifer Carrigan, a senior at Chester High School, and her prom date died, although authorities had made an arrest in the case. Autopsies were scheduled for Tuesday at the Washoe County Medical Examiner's Office in Nevada.

The Glenn County Sheriff's Department said Furtado had traveled from Willows, where he was a high school senior, to Chester to take Carrigan to her senior prom.

Deputies arrested 18-year-old Reyes Carillo in the deaths of the two teens, said Plumas County Sheriff's Patrol Commander Gerry Hendrick. He said Carillo previously dated Jennifer Carrigan.