SHERIDAN — Two single-vehicle accidents occurred in Sheridan this week — one fatal and the other resulting in critical injuries.

The first occurred with a single vehicle rollover Tuesday just after 4 p.m. on Beatty Gulch Road at mile marker 0.5. The driver was ejected from the vehicle, and the Sheridan County Sheriff’s Office is still investigating the cause of the rollover.

The driver was treated at the hospital for sustained injuries.

The second accident involved a single motorcycle Wednesday morning around 7 a.m. on Interstate 90 westbound at mile marker 31.

Wyoming Highway Patrol responded to the accident and said the motorcycle was headed west, ran off the road to the right and skipped off the guardrail about four times.

The crash is still under investigation by WHP as to the official cause of the accident.

The rider, 69-year-old Coy Collins of Grants Pass, Oregon, suffered significant head trauma despite wearing a helmet.

Paramedics responded and pronounced Collins dead at the scene.

Troopers learned from Collins’ wife that he had left Sturgis, South Dakota, at 2:30 a.m. Wednesday and was headed west back to Oregon.

Sturgis is currently hosting its 78th annual motorcycle rally, a 10-day event in which hundreds of thousands of motorcycle enthusiasts from around the world gather in the city.

An autopsy was conducted Wednesday afternoon to determine if any medical or other conditions contributed to the fatal crash.

Troopers said they are not investigating cellphone usage or intoxication at this time.