A serious collision between a motorcycle and a pickup truck sent a rider to a local trauma center with life-threatening injuries Monday afternoon in Santee, according to the San Diego County Sheriff's Office.

Deputies from the Santee Station responded to multiple 9-1-1 calls around 1:50 p.m. reporting the crash at North Magnolia Avenue and the on-ramp to State Route 67/52. When they arrived, they found the motorcyclist on a nearby grassy embankment, critically injured.

A bystander had already begun providing first aid at the scene. Responding deputies joined in, applying a tourniquet to help control the rider's bleeding before paramedics transported the victim to a local trauma center.

The driver of the pickup truck remained at the scene and was evaluated and treated by emergency medical personnel. Authorities say drugs and/or alcohol are suspected to be contributing factors in the collision.

The Santee Sheriff's Traffic Unit is actively investigating. Anyone who witnessed the crash or has additional information is urged to contact the Santee Sheriff's Station.