A deputy sheriff on patrol in Cupertino, California, Sunday crossed the double-yellow line on Steven Canyon Road and hit a group of riders shortly before 10:30 a.m.

According to California Highway Patrol Officer Todd Thibodeau, whose team is investigating the incident, two cyclists, Kristy Gough, 30 of San Leandro and Matt Peterson, 29, of San Francisco died, the San Francisco Chronicle reported. A 20-year-old man was seriously injured. He was immediately transported at Stanford University Medical Center where he was listed in critical condition Sunday night. The fourth rider was not hurt.

Sgt. Don Morrissey, a spokesperson for the Sheriff’s Department said the unidentified deputy was driving northbound when his white cruiser accidentally crossed over the double line between Montebello and Ricardo roads and hit the cyclists. The deputy immediately began to assist the bicyclists and called for medical aid.

The deputy, who has worked for the sheriff’s department for about 18 months, will be placed on paid administrative leave pending the outcome of the investigation.

“The deputy is very distraught over this right now. It’s devastating for everybody involved,” Morrissey said, according to the San Francisco Chronicle.

Fatal crashes are rare for the sheriff’s department, even though deputies often drive as many as 200 miles in a single shift.

The last fatal crash involving a sheriff's patrol car happened in 1994, when a deputy trying to keep a suspect from running struck and killed the man near the intersection of West San Carlos and Bascom Avenue. The deputy was cleared of wrongdoing.