A 69-year-old Massachusetts man died Sunday from “blunt force injury to his head and trunk,” presumably after his bicycle crashed on Tucker Avenue at Larson Street.

That’s according to the King County Medical Examiner’s office, which determined the cause of death and ruled it an accident. But what caused his bicycle to crash is still being investigated.

The bicyclist was identified by the Sheriff’s Department as Richard Conley, 69, of Woburn, Mass. Sheriff Bill Cumming said the incident is not believed to have been caused by road conditions or traffic. “He fell down inexplicably,” Cumming said.

Conley was bicycling with a friend toward town when the incident occurred. He was not wearing a bicycle helmet, Cumming said.

A 911 call was placed at 4:23 p.m. Conley was airlifted to Harborview Medical Center. He died Sunday at 9 a.m.