Police are investigating a case in which a confrontation between a cyclist and an errant driver turned violent near Potrero Hill. A woman leaving work Tuesday was maced by the driver of passing car, after she attempted to confront the driver for almost hitting her.

Danica Helb was riding her bike on 16th Street between Mississippi and Owens Street, reports Streetsblog, when a black Cadillac passed her within six inches and at high speed. The 35-year-old scientist was leaving her lab at San Francisco General Hospital and riding to her office — a ride she had done on many previous occasions — when the incident occurred.

Helb explained, “[You] lose the designated bike lane and there’s no shoulder,” she noted. The Cadillac sped ahead of her with much less than the legal three-foot buffer between them, and shaken by the near miss, Helb told the Examiner that she then pedaled to where the Cadillac had stopped at a red light in order to "calmly" tell the driver to be more careful when passing people on bicycles.

After knocking on the car window, the driver, who according to Helb's witness statement to police was a 45- to 55-year-old African American woman, yelled at her to "go away."

“She rolled down the window and took out a mace/pepper spray canister and told me ‘I was going to get it,'" Helb said in her statement. She admits that after the driver yelled at her she yelled back. It was when she began to back up to take a photo of the car's license plate that the driver allegedly sprayed her mace can toward the window, mostly missing her, however some spray was blown toward her by the wind.

“It got into my throat and eyes,” Helb told Streetsblog. Two witnesses reportedly came forward to corroborate Helb's version of the events, and one of them got in touch with the publication.

“The cyclist was really shaken up and surprised,” said the witness who only gave her first name of Sarah. “It was unwarranted the way she was treated by the person in the vehicle.”

SFPD Officer Carlos Manfredi told the Examiner that the incident is being investigated as a potential case of battery, and that the driver could also face charges for violating California's three-foot law.

“When you drive, you operate a weapon, as a cyclist, we’re completely unprotected, and vulnerable on the road," Helb told the paper. "I’m still a little shaken up."

Still, Manfredi cautions, "I don’t recommend knocking on a window to advise a driver…you never know when the driver will interpret your actions as violent, even if you just want to say ‘hey,’ you’re in violation."

Related: Video: Driver Cuts Off Cyclist, Responds With Profanity And Threats