A 69-year-old Massachusetts man died Sunday after crashing on his bicycle a day earlier on Tucker Avenue at Larson Street.

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 and treated for severe head injuries. He died Sunday at 9 a.m. The cause of death had not been determined by Monday.