A motorcyclist hit the back of a pickup truck before veering into the oncoming lane and striking another vehicle in Casco Thursday afternoon.

Windham resident Kevin Lavoie, 21, was driving his Harley Davidson west on Route 302 when he hit the other vehicles around 4 p.m., said Kerry Joyce, patrol captain at the Cumberland County Sherriff’s Office. Lavoie was not wearing a helmet and was transported by Life Flight to Maine Medical Center with life-threatening injuries, Joyce said in a statement around 7 p.m.

“Speed is believed to be a contributing factor in this crash,” Joyce said in the statement.

The driver of the second car Lavoie hit, 44-year-old Windham resident Jeffrey Lynds, was taken by ambulance to Bridgton Hospital for minor injuries, Joyce said.

It was not immediately clear whether the driver of the pickup truck Lavoie initially hit, 69-year-old Casco resident Dennis Butterfield, was injured. Joyce did not mention Butterfield’s condition in the statement.

Deputy Erik Richard said he believed Butterfield was uninjured, but he could not say for sure without seeing the final report. Richard said he was briefly on the scene when reached by phone Thursday evening.

The crash closed a stretch of Route 302 near Lakewood Road for several hours, but the street was reopened before 7 p.m., the Cumberland County Regional Communications Center said in another statement.

The cause of the crash remains under investigation by the sheriff’s office.