KATY -

A 28-year-old man died after a high-speed motorcycle crash in west Harris County.

The man was riding eastbound down Kingsland Boulevard just west of the Grand Parkway around 10:45 p.m. Tuesday. Deputies said he may have been going around 100 mph when he slammed into the back of a green minivan. The woman in the minivan was not hurt.

The man on the motorcycle was thrown from his bike and suffered a massive head injury.

A medical helicopter took him to Memorial Hermann Hospital, where he died of his injuries.

Deputies said the 28-year-old victim was wearing a helmet, but it was not properly secured. They believe the chin straps were too loose.

It is unclear if the man was under the influence when he crashed.

Deputies said toxicology tests will determine that.