Police arrest man suspected of Critical Mass vandalism

Wearing a T-shirt saying, “Non-violence is our strength,” a Critical Mass cyclist vandalizes a Zipcar with a metal bike lock in a video posted by YouTube user Bike42363. Wearing a T-shirt saying, “Non-violence is our strength,” a Critical Mass cyclist vandalizes a Zipcar with a metal bike lock in a video posted by YouTube user Bike42363. Photo: YouTube / Bike42363 Photo: YouTube / Bike42363 Image 1 of / 23 Caption Close Police arrest man suspected of Critical Mass vandalism 1 / 23 Back to Gallery

San Francisco police arrested a man Saturday evening who they believe used a U-lock to smash a driver’s window during last month’s Critical Mass bike ride, an incident seen far and wide after video of the incident went viral.

Bike-mounted officers were working outside of AT&T Park when they spotted the suspect, identified as 39-year-old Ian Hespelt of San Francisco, riding his bicycle near McCovey Cove, said Officer Grace Gatpandan, a police spokeswoman.

The officers noticed that Hespelt matched the description of the man in the video seen swinging the lock, and his bike was a match too, Gatpandan said. Hespelt was detained and taken to the Southern Station for questioning.

The trouble began Aug. 28 around 8:15 p.m., when the monthly Critical Mass ride was making its way through the Marina.

In the video, about a dozen cyclists can be seen riding against traffic on Marina Boulevard near Lyon Street when one cyclist stops in front of a dark-colored station wagon and yells, “Hey! Stop that! No, no, no, no, no.”

As more cyclists surround the Zipcar, one man accuses the driver of hitting his bike while others hurl insults and expletives. The driver eventually begins to back up and tries to drive around the group, only to be blocked again.

Finally, the driver slowly pushes past the group when one rider, purported to be Hespelt, begins swinging his bike lock at the car, smashing the driver’s side window.

Critical Mass is a protest ride that happens on the last Friday of every month in San Francisco. The rides began in the city in 1992 but are now held in almost 300 cities around the world, according to the organization’s website.

SF Critical Mass’ website tells participants: “Don’t ride into oncoming traffic on the wrong side of the road” and “Don’t pick fights with motorists, even if they’re itching for one.”

In the May-June issue of the American Postal Worker magazine, a publication of the American Postal Workers Union, Hespelt was identified as “a Macy’s employee in San Francisco and a shop steward for the United Food and Commercial Workers Union” who was a frequent participant in union protests.

On Saturday, after investigators finished questioning Hespelt, he was arrested on suspicion of assault with a deadly weapon, vandalism, false imprisonment, and maliciously and willfully throwing a substance at a vehicle, all felonies. He was also booked on a misdemeanor charge of inciting a riot, Gatpandan said.

Kale Williams is a San Francisco Chronicle staff writer. E-mail: kwilliams@sfchronicle.com Twitter: @sfkale