SAN JOSE — 49ers cornerback Chris Culliver, who went on an infamous anti-gay rant at last year’s Super Bowl, now is accused in a civil suit of using a racial slur and threatening a teenager with brass knuckles during a confrontation that ended with his March arrest for hit-and-run and weapons offenses.

The suit — which seeks unspecified damages — was filed in Santa Clara County Superior Court in April by Marc Santos, whose vehicle was hit during Culliver’s alleged attempt to drive away after authorities say he hit a bicyclist. The suit’s details add to an unflattering picture of off-field conduct painted through police reports the past two years. As previously reported by this newspaper, the 49ers have had more player arrests than any other NFL team since 2012, including Aldon Smith’s alleged fake bomb threat made at LAX last month.

Police say Santos had blocked Culliver’s Ford Mustang in a cul-de-sac with his vehicle until San Jose police arrived and arrested the football player.

Speaking publicly for the first time, Santos told this newspaper that Culliver was hostile, profane, repeatedly tried to leave the scene and at one point threatened Santos’ 15-year-old son with brass knuckles on his right hand.

“He kept cussing at us to let him go,” Santos said. “I said, ‘You’re not going anywhere.’ “

At some point, Santos said, Culliver directed an ethnic slur at him and his family, who are Latino.

Culliver has pleaded not guilty to misdemeanor hit-and-run and a felony weapons charge for the brass knuckles, which were found in his car after his arrest. So far, neither police nor prosecutors have presented evidence to corroborate Santos’ allegations of a physical threat.

That absence partially explains the motivation for the lawsuit, said Braid Pezzaglia, the attorney representing the Santos family.

“The criminal action does not include any of the conduct against our clients,” Pezzaglia said. “He put our client and his family through a lot, and they don’t want to see him get a slap on the wrist.”

A 49ers spokesman said the team cannot comment because it is an ongoing legal matter. Teddy Palmer, Culliver’s publicist, said Thursday he knew nothing about the civil suit and that his client also would not speak on the matter.

Culliver not only remains a member of the organization, but he is considered a top candidate to be a starting cornerback position next season when the team moves into Levi’s Stadium in Santa Clara. Culliver, 25, a third-round pick by the 49ers in 2011, missed all last season with a knee injury.

He already was a controversial figure after making homophobic comments before the 2013 Super Bowl, saying in a Media Day interview that gay athletes wouldn’t be welcome in the 49ers’ locker room. Culliver apologized and took steps to rehabilitate his image by reaching out to an LGBT organization and receiving widespread praise for his personal growth.

But just days after telling this newspaper how much he had changed, Culliver was arrested. It capped a fracas that began around 10:20 a.m. March 28, when a bicyclist was struck in the intersection of Tully Road and South Seventh Street by a white Mustang that fled the scene, according to police.

Santos witnessed the collision, saying the bicyclist had been at a crosswalk pushing the signal button when he was hit and flew “at least 4 feet into the air.” The cyclist suffered minor injuries.

Moments later, he said the Mustang hit the driver’s side of Santos’ Yukon Denali SUV at Tenth Street.

“When he hit us, the light was red,” Santos said. “Then when it turned green he takes off.”

Santos, whose wife called 911 as his three children — ages 15, 4 and 2 months — sat in the back seat, followed the Mustang to get a look at a license plate number, but the dealer plates were still on. “I didn’t know if he killed the guy on the bicycle,” Santos said.

He tailed the Mustang onto Senter Road, and when it got to the area of Mekler Court, he used his SUV to block the Mustang into a cul-de-sac and soon was joined by the occupants of a pickup truck who also witnessed the bicyclist get hit.

Santos said Culliver, whom he did not recognize until seeing news reports later in the day, tried several times to back up his car and drive toward the impromptu blockade to get the vehicles to move, to no avail. That’s when Culliver, Santos said, pulled out a black backpack, reached his hand in, and charged at his son wearing the brass knuckles on his right hand.

Santos said no physical contact was made. Minutes later, police arrived.

It was just one of a string of incidents that have embarrassed the 49ers. The team has had players arrested nine times since 2012 — the most in the NFL during that span, according to a review conducted by this newspaper. The latest occurred on April 13, when star outside linebacker Aldon Smith was arrested on suspicion of making a false bomb threat at Los Angeles International Airport.

At a news conference last month, General Manager Trent Baalke spoke generally about how the team believes in supporting players, without defending any specific actions.

“I’m adamant in my thoughts: This is a good group of men,” Baalke said. “Have they made some mistakes? Absolutely they’ve made some mistakes. And I’m not going to sit up here and defend them. They have to learn from those mistakes.”

Contact Robert Salonga at rsalonga@mercurynews.com. Contact Mark Emmons at memmons@mercurynews.com.