A California doctor is dead after the driver of a car allegedly struck and stabbed him as he was cycling on the Pacific Coast Highway on Wednesday afternoon, police say.

Michael John Mammone, 58, was cycling on the Pacific Coast Highway when he was reportedly struck from behind by a northbound vehicle, according to a release from the Orange County Sheriff’s Department. For unknown reasons, the driver of the vehicle, Vanroy Evan Smith, 39, reportedly exited the car and began stabbing Mammone with a knife. Bystanders who witnessed the incident intervened and detained Smith until authorities arrived. (RELATED: Video Shows Pipe-Wielding Man Charge At Driver On Freeway)

The bicyclist killed has been identified as Michael John Mammone, a doctor at Providence Mission Hospital Laguna Beach. https://t.co/qNbK0Twx1j

— FOX 11 Los Angeles (@FOXLA) February 2, 2023

Mammone, an emergency room physician at the nearby Providence Mission Hospital in Laguna Beach, often rode his bike to work. He was rushed to a local hospital for his injuries but was later pronounced dead, CBS reported.

“That’s the irony of this whole thing. If a patient was brought in his condition he would have done everything he could to save that person. He has saved so many lives here, and he died very close to where he saved hundreds of lives,” said cardiologist and former co-worker Dr. Dawn Aatwal told Fox News 11.

“We are stunned by this devastating tragedy. The entire Mission Hospital family is grieving over the loss of an incredible physician and friend. We will honor Dr. Mammone’s dedication to our community and passion for medicine by continuing to provide exceptional care,” the hospital said in a release upon the news of Mammone’s death per the outlet.

Smith was transferred to the Orange County Jail on suspicion of murder and is due to appear in court Friday, according to CBS News.