A 67-year-old man was beaten and robbed in the parking lot of the Graton Resort & Casino in Rohnert Park Tuesday morning, an attack that left him with severe head trauma, the Sonoma County Sheriff's Office said.

Deputies were called to the scene around 6:30 a.m. and found that he had been struck in the head with an unknown weapon and robbed of an unknown amount of cash and other property, according to a departmental release.

The man, whom deputies did not identify, told investigators from the Violent Crimes Unit that at least two people were involved in the assault.

He was transported to Santa Rosa Memorial Hospital.

Deputies and casino security are investigating the attack.

Candidates for Sonoma County Sheriff

Name: Mark Essick

Age: 48

Career: Sonoma County Sheriff’s Office for 23 years; had visible roles representing the Sheriff’s Office in the past; was a member of the community task force created in the wake of the 2013 Andy Lopez shooting

Name: Ernesto Olivares

Age: 60

Career: Santa Rosa Police Department for 30 years; Santa Rosa City Councilman has garnered endorsements from Rep. Mike Thompson, D-St. Helena, and fellow Santa Rosa councilmen John Sawyer and Tom Schwedhelm

Name: John Mutz

Age: 68

Career: Los Angeles Police Department for 25 years; after retiring in 1999, Mutz developed a mediation program for racial profiling cases for the Los Angeles Police Department