SAN FRANCISCO (KPIX 5) — A man claims he was sexually assaulted at a San Francisco health club, which then tried to cover it up by canceling his membership after he called police.

The assault allegedly happened a few months ago at the Equinox Sports Club on Market Street.

Colin Heilbut says he has done roughly 1,000 hours of yoga in his lifetime. But he says at the Equinox, he got a yoga lesson he’ll never forget.

“As soon as we walked in he asked me to spread my legs against the wall,” said Heilbut. “It’s not related to any yoga pose I’ve ever done.”

Heilbut said a yoga teacher named Kevin Nguyen took a sudden interest in him in August.

First, he says there was an inappropriate touch that happened in class.

“He cupped my testicles. And I didn’t see that coming and I didn’t quite know what to think,” Heilbut said. “But I also didn’t think it was anything more than a horrific accident.”

Heilbut said when Nguyen offered him private lessons after class the touching turned to sexual assault. He said Nguyen was very selectively picking poses that had an unnecessary amount of physical contact.

A letter he wrote to Equinox states: “There was unwanted contact of my genitals and buttocks … unwanted body massage … unusually prolonged physical contact.”

“That’s when I noticed I guess what I would describe as a bulge in his pants,” Heilbut said.

And then he says Nguyen made a sound. “Low, almost a subdued — like he was trying not to make it but couldn’t help himself — moan that I would associate with an orgasm,” Heilbut said.

Nguyen told KPIX 5 that the allegations are unfounded.

Heilbut complained to Equinox and filed a police report. He said police warned him that it would be tough to prosecute, even though surveillance video captured the yoga lesson.

“The sergeant said the actions he viewed on the camera reflected incredibly unprofessional, bizarre activities by this instructor,” Heilbut said.

Police also told Heilbut that Nguyen had been fired but declined to bring charges against him.

That’s when Equinox called and dealt Heilbut another blow.

Heilbut said the gym told him: “You’re banned from the gym. We’ve decided to terminate your membership.”

Heilbut’s lawyer, civil rights attorney Larry Organ, says it’s a classic case of retaliation.

Organ said, “You can’t blame the victim. And that’s exactly what they’re doing. This is what the hashtag #MeToo movement’s all about.”

Heilbut has filed a lawsuit demanding that Equinox “better train staff on appropriate responses to sexual harassment” and “cease terminating the memberships of persons who complain about sexual harassment.”

In a statement, Equinox said both police and their internal officials “investigated these allegations and found them to be unfounded … We intend to defend vigorously against the claims in the lawsuit.”

But Heilbut says he’s since heard of another lawsuit and several other complaints against Equinox that he fears point to a pattern.

“Equinox is supporting sexual assault by creating this culture, by having this policy of punishing anyone who speaks out,” Heilbut said.

The San Francisco Human Rights Commission is also investigating the allegations.