Hawai'i County police said they believe speed and alcohol were factors in a motorcycle crash Saturday that killed a 27-year-old Kea'au man.

Puna officers said Joshua Glenn Vanhook was operating a 1985 Yamaha motorcycle and was traveling south on Route 137 about 4:30 p.m. when he lost control and ran off the right side of the highway, just before Pohiki Road.

Officers said he was not wearing a helmet.

Vanhook was taken to Hilo Medical Center, where he was pronounced dead at 8 p.m.

An autopsy has been ordered.

Police are asking that the anonymous male caller who called 911 or anyone else with information regarding this crash to call Officer Clarence Davies at 808-961-8118.

This is the sixth traffic fatality on the Big Island this year compared to 11 at the same time last year.