WALNUT CREEK — A motorcyclist killed in a horrific crash along Interstate 680 just north of Danville may have been racing two other vehicles at speeds of 80-100 mph before the fatal wreck, police said Monday.

Authorities identified the man as 31-year-old Joseph Botsford of Walnut Creek. He died instantly and another man was hospitalized in the Sunday wreck, which happened at 5:48 p.m. in the northbound direction between the Livorna Road and Rudgear Road exits.

Several witnesses reported Sunday that the motorcycle and another car were driving excessively fast, a claim reiterated by a CHP spokesman on Monday.

“We believe there may have been a speed contest and that at least three cars were involved and going anywhere from 80 to 100 mph,” CHP Officer John Fransen said. “It’s a call to all motorcyclists and other drivers that these are not toys.”

Fransen said the motorcycle was racing a black Nissan 380 Z ï»¿and that as many as three other vehicles, one of them a motorcycle, may have been racing, too.

A Walnut Creek woman who was first upon the scene and saw bits of the wreck said Sunday that “there were definitely two motorcycles that were not being safe.”

“He had his right hand on the bar and his left hand on the seat,” Alexandra Crowe also said of the motorcyclist.ï»¿ “And he kept looking behind him.”

The motorcycle and Nissan collided, Fransen said, sending the Nissan into an embankment, where it burst into flames. That driver escaped the car and was taken by ambulance to John Muir Medical Center with serious injuries, CHP Sgt. Franco Dalao said. The CHP did not have an update on his condition early Monday morning.

Contra Costa Fire Protection District crews put out the fire before it spread to the hillside along the freeway.

After the initial collision, the motorcycle hit a Mustang and Botsford was ejected, landing on a Silverado, Fransen said. The Silverado did not appear to be involved in the racing, Fransen said. Police were still investigating the Mustang’s role, if any, in the collision, Fransen said.

Parts of the motorcycle, including what appeared to be a sizable piece of its midsection, was strewed for at least a quarter-mile in the northbound direction of I-680 where the wreck occurred.

Contact Rick Hurd at 925-945-4780 and Natalie Neysa Alund at 510-293-2469. Follow Rick at Twitter.com/3rdERH and follow Natalie at Twitter.com/nataliealund.