A well-known Mendocino County psychiatrist was struck and killed by a big rig Friday morning while riding his bicycle near downtown Ukiah.

Douglas Rosoff, 56, of Ukiah, was an avid cyclist known for his regular morning, pre-work rides.

He also was a respected figure in Mendocino County government, where he was the chief psychiatrist in the county's mental health division until a 2011 move to work for the Veterans Administration.

He died shortly before 8 a.m. on his regular East Gobbi Street route, apparently as he and the trucker approached the South Orchard Street intersection.

Preliminary investigation indicated the westbound trucker turned right from East Gobbi onto northbound South Orchard, colliding with Rosoff, who also was westbound, CHP personnel said.

Ukiah Police Capt. Justin Wyatt, whose agency is leading the investigation, declined to release further details or the name of the truck driver. Wyatt did not clarify whether the driver saw Rosoff in advance of the crash or not.

A female companion traveling behind Rosoff was unhurt, Wyatt said, though witnesses described her as distraught.

The 7:57 a.m. collision and its aftermath were highly visible to commute-hour traffic along the busy road.

Among those stopped in traffic immediately afterward was Tim Walsh, owner of Ukiah Schwinn/Ukiah Bike Center a few blocks down East Gobbi Street from the accident site.

"I'm just devastated," Walsh said, describing Rosoff as "a heck of a nice guy."

Former colleagues in Mendocino County government echoed those sentiments Friday. Rosoff oversaw care and cases for adult and juvenile patients, including those in the criminal justice system, officials said.

"He was very well respected," said Stacey Cryer, director of the county's health and human services agency, which includes the mental health division.

"He was probably one of the finest human beings I've ever met," said sheriff's Capt. Tim Pearce, who commands the jail division and worked with Rosoff for 15 years. Rosoff continued to work with juvenile hall detainees after his job move. Pearce called him the "heart and soul of the county's mental health system."

"He was an advocate for all those with mental health issues," said sheriff's Capt. Kurt Smallcomb.

As word filtered down of his death Friday, there was an outpouring of grief and sadness among his former co-workers, Cryer said.

"That goes throughout the county," she said. "This is a community loss for sure."

Rosoff's family members were not available for comment Friday.

East Gobbi Street is a key bicycling route because of bike lanes that run the length of the road, over Highway 101 and to the street's end about a quarter-mile east of the highway.

"It's one of the more regularly and heavily traveled bike routes going east and west," said Dave Minsinger, owner of Dave's Bike Shop, located across the street from Walsh's store and, like Walsh's, just blocks west of the crash scene.

He and Walsh said customers coming into the shop were alarmed by the news Friday, many of them having seen the road closure and crash scene.

Several of Rosoff's co-workers were in the vicinity, as well.

Walsh said he saw the cyclist face down on the pavement and said he was wearing bright riding gear and a helmet. But he said he was not prepared to cast blame until he knew something about how it had happened.

"I have had several people open their car doors on me when I'm passing a parked car. I've had people hop right off of the curb, and I've had cyclists go through intersections without looking," Walsh said. "It happens, you know?

"And I don't know what the heck the cure is for it. There isn't a cure, unless it's just heightened awareness."