Two men died in two separate crashes on Hawaii island over the weekend.

Shortly before 7:50 p.m. Friday in Kealakekua, police said, a 1992 Mazda two-door convertible sedan operated by Robert Weeks, 48, of Hilo was traveling north on Highway 11 when he failed to negotiate a right curve near the mile 99 marker.

The vehicle ran off the roadway and overturned into an embankment. Paramedics transported Weeks to Hilo Community Hospital, where he was pronounced dead at 1:54 a.m. Saturday.

Police said excessive speed and inattention were involved.

The second fatal crash involved a motorcycle and a sedan in Kailua-Kona.

Police said Elvis Sheppard, 43, of Kailua-Kona was killed in the broadside collision.

At about 7:30 p.m. a 2016 Honda motorcycle operated by Sheppard was traveling east on Hinalani Street when a 2006 Kia four-door sedan operated by a 61-year-old man, also of Kailua-Kona, failed to yield the right of way to the motorcycle.

Police said the sedan driver broadsided Sheppard, who was making a left turn onto Hinalani Street from Kamanu Street.

Paramedics transported Sheppard to Kona Community Hospital in critical condition. He died at 10:24 a.m. Saturday.

Police said the 61-year-old driver was uninjured.

Excessive speed and inattention were factors in the crash.

Weeks’ and Sheppard’s deaths were the Big Island’s eighth and ninth traffic-­related fatalities of the year, respectively, compared with 10 at the same time last year. Autopsies are expected to be conducted to determine the exact causes of death.

The Hawaii Police Department’s Traffic Enforcement Unit has initiated a negligent-homicide investigation into the Kailua-Kona crash. Anyone who witnessed the collision is asked to call Officer Justin Hooser at 326-4646.

Police are also asking for individuals who witnessed the Kealakekua crash to call Officer Christopher Kapua-Allison at 326-4646.

Tipsters who have information on either case also may call CrimeStoppers at 961-8300.