SAN DIEGO — A 20-year-old motorcyclist was killed in a crash along Interstate 5 in Oceanside this week, authorities said.

Griffin Williams of Lake Forest, California, was driving on I-5 just north of Las Pulgas Road around 12:30 a.m. Wednesday when he lost control of his motorcycle while traveling at a high rate of speed, according to the San Diego County Medical Examiner’s Office. Williams crashed into the back of a horse trailer attached to a truck that was in front of him on the freeway.

The driver of the truck told police that he immediately pulled over and noticed smoke coming out of the back of the horse trailer. The man looked into the attached trailer, found Williams inside, and called 911.

Officers with California Highway Patrol and EMS were called to the scene but Williams was pronounced dead without medical intervention due to “obvious fatal injuries.”

The matter remains under investigation by officials.