A 39-year-old man has been charged with murder after allegedly striking and fatally stabbing an emergency room doctor who was riding his bicycle along Pacific Coast Highway in Dana Point earlier this week.

The incident occurred around 3 p.m. Wednesday at the intersection of PCH and Crown Valley Parkway.

Vanroy Smith, of Long Beach, allegedly rammed the back of Michael Mammone’s bike with his white Lexus.

After the crash, Smith got out of his vehicle and allegedly stabbed Mammone, 58, several times as witnesses tried to help the injured man, officials said.

Smith was detained by witnesses at the scene until law enforcement arrived.

Mammone, who worked as an emergency doctor at Providence Mission Hospital in Laguna Beach, died at a hospital.

Smith was charged with one count of murder with a special enhancement that he used a deadly weapon, a knife, during the crime, according to the Orange County District Attorney’s Office.

He pleaded not guilty during a court appearance Friday and is due back in court on Feb. 16. He is being held on $1 million bail.

Smith faces a maximum sentence of 25 years to life in prison, plus one year, if convicted as charged.

The two men did not know each other, and the motive behind the crime remains unclear.

“An innocent man is dead because he took a bike ride to enjoy a beautiful California day along the beach and he was hit with a car and stabbed to death by someone he apparently never met,” District Attorney Todd Spitzer said Friday. “The murder of a complete stranger in broad daylight for what appears to be absolutely no reason is the stuff of nightmares. This unspeakable act of violence will forever haunt those who were forced to witness it and it will forever haunt all of those who loved Dr. Mammone.”