A man was kidnapped on the College of Marin campus in Kentfield and sexually assaulted at gunpoint in the Mill Valley area, authorities said.

The incident began at about 8:15 p.m. Thursday in parking lot 13 of the campus, the college reported. The victim got into his car after a class and discovered that an armed man was in the back seat.

The man ordered the victim to drive off. They drove to a neighborhood in Tamalpais Valley, where the attacker sexually assaulted the victim, said sheriff's Sgt. Nina Snyder. The victim was able to escape the car and get help.

The attacker left the victim's car where it was and escaped.

The attacker was described as black, heavy set and about 6 feet to 6 feet 2 inches tall. His weight was estimated at 200 to 235 pounds and he was wearing a black sweater and black gloves.

The victim was taken to a hospital for treatment. His age was not released.

Authorities did not specify whether the victim was enrolled for college credit or participating in another type of program.

Parking lot 13 is on the south side of the campus near the Physical Education Center and the Child Study Center.

The college published an alert about the crime on its website and other platforms on Friday.

Greg Nelson, the vice president for college operations, said the school has increased security on campus, but he declined to comment on the police department's staffing levels or schedules.

"This can have an affect on the operational integrity of our Police Department," he said in an email.

The campus does not have security surveillance cameras, but a plan was already in the works to install them, he said.

"We have stepped up our police presence on campus," he said. "We will continue to do this in order to ensure our campus community has a safe and secure environment. We have also added portable light towers to increase lighting and we are asking students and staff to walk in pairs or ask for police escorts if needed."

The campus police department is a 24-hour operation that includes the chief, a sergeant and eight officers, according to its website. It also has three cadets and an administrative aide. Dispatch services are provided by the Fairfax Police Department.

In addition, the Marin County Sheriff's Office maintains a station across the street from the campus on Sir Francis Drake Boulevard.

Anyone with potential information about a suspect in the sexual assault case can call the Marin County Sheriff's Office 479-2311 or College of Marin Police Department 485-9696.

Rape and attempted rape cases are rare on College of Marin campuses. The college police reported one rape case between 2003 and 2012, according to the California Department of Justice. It occurred in 2006, but the statistics do not specify whether it happened on the Kentfield campus or the Novato campus.

Twelve assaults were reported over that period.

Statistics for 2013 were not available.

Contact Gary Klien via email at gklien@marinij.com or https://twitter.com/GaryKlien