A California man was killed Wednesday in a rage-filled incident that has officials trying to find a motive.

In the final moments of his life,  Dr. Michael Mammone was riding his bicycle north on the Pacific Coast Highway near Dana Point, according to a news release from the Orange County Sheriff’s Department.

He was struck from behind by a northbound car and flung to the pavement.

At that point, police allege that Vanroy Evan Smith, 39, of Long Beach got out of his vehicle and stabbed the 58-year-old with a knife.

Mammone was taken to a hospital, where he was pronounced dead. Smith was taken to Orange County Jail and locked up on suspicion of murder. A knife was recovered at the scene.

Bystanders intervened, police said.

"There were actually locals that were able to detain him until police arrived," OCSD Sergeant Mike Woodruff said, according to CBS.

Witnesses said Smith had a BB gun as he approached Mammone.

Officials said the reason for the stabbing is unclear.

Murder charge filed in Dana Point bicyclist death. Vanroy Evan Smith, 39, has been charged by OCDA with killing Dr. Michael Mammone with "malice aforethought." An enhancement was added for use of a knife. Smith is expected in court later today. @KTLA pic.twitter.com/ws3bM3sICZ

— Chip Yost (@ChipYost) February 3, 2023

“As of right now we currently don’t truly understand the why… as far as motivation and any type of relationship. Investigators are keeping all options open to check those boxes if you will, to make sure they don’t leave anything uncovered," Woodruff said.  according to KTLA-TV.

Orange County District Attorney Todd Spitzer deplored Mammone’s death, according to KABC-TV.

"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," he said.

"The murder of a complete stranger in broad daylight for what appears to be absolutely no reason is the stuff of nightmares,” he said.

A neighborhood camera caught the incident on video.

WARNING: This post contains images which some may find disturbing. 

Laguna Beach, CA: Neighborhood cam captures the moment Dr. Michael John Mammone (58) was struck by a vehicle and stabbed. The suspect Vanroy Evan Smith (39) of Long Beach was taken into custody for suspicion of murder. Knife found at the scene. No motive at this time. pic.twitter.com/1TIpfvkqz5

— DeL2000 (@DeL2000) February 3, 2023

A report in the  New York Post referenced a comment from a neighbor who was not identified claiming that Smith was overheard to use the words “white privilege” at one point.

Providence Mission Hospital, where Mammone was an emergency room doctor, released a statement on Mammone's death.

The driver, a black male identified as 39-year-old Vanroy Evan Smith of Long Beach, quickly exited his vehicle and stabbed the victim.

The victim, identified as 58-year-old Michael John Mammone, a Laguna Beach ER doctor, died at the hospital. pic.twitter.com/vTnlWsdA1m

— VIOLET (@violetssmith) February 3, 2023

"We are stunned by this devastating tragedy. The entire Mission Hospital family is grieving over the loss of an incredible physician and friend,” the statement said.

This article appeared originally on The Western Journal.