Millionaire tech mogul Gurbaksh Chahal violated his probation for a domestic violence conviction when he allegedly attacked a girlfriend one year after brutally beating a different woman in the same San Francisco penthouse, a judge ruled Friday.

San Francisco Superior Court Judge Tracie Brown ordered Chahal, 34, to surrender his passports to the court by Monday. At a sentencing hearing scheduled for Aug. 12, he could be sent to jail or have his probation extended largely depending on what his probation officer recommends.

Police first arrested the CEO of advertising company Gravity4 after he attacked his former girlfriend Aug. 5, 2013, inside his Rincon Hill penthouse.

Officers seized a surveillance video they said shows him beating and kicking the woman more than 100 times, and prosecutors charged him with 47 felony counts of domestic-violence related offenses. But a judge ruled the video was unlawfully seized and suppressed it from evidence.

With prosecutors barred from using the 30-minute video, Chahal eventually struck a deal and pleaded guilty to two misdemeanor charges of battery and domestic violence, and was placed on probation. After the plea, the board of directors of San Francisco advertising company RadiumOne forced out Chahal as CEO.

In a victory for the prosecution, Brown ruled Friday the video could be entered into evidence — and thus the public record — in determining whether Chahal violated his probation for a second alleged attack on Sept. 17, 2014. In that confrontation, prosecutors said Chahal kicked a South Korean woman, whom he was dating, roughly 10 times and later conspired with associates to dissuade her from talking to the police by threatening to report her to immigration authorities, prosecutors said.

“The defendant knew he was in trouble and immediately rallied the troops and used the enormous resources at his disposal,” Assistant District Attorney O’Bryan Kenney said in court Friday of Chahal, who by age 25 had sold two advertising companies he had founded for more than $300 million.

Case similarities

Kenney, calling the similarity between the 2013 and 2014 episodes “remarkable,” argued that the video showed a pattern of abuse. In both cases, prosecutors and police said Chahal was incensed and accused the women of infidelity.

“I think it’s very important you find that video admissible, and you should watch it,” Kenney told the judge in remarks that were punctuated by audible sighs and whispers from Chahal’s entourage of relatives and supporters. “In the very room, in the very bed where he did it before ... the pattern here is unmistakable.”

The second alleged victim, whom The Chronicle is not naming, stunned prosecutors and Chahal’s defense team when she returned to South Korea in the midst of the litigation. Both sides said her failure to appear has hurt their cases, with defense attorney James Lassart arguing that Chahal had a constitutional right to confront his accuser in the probation hearing.

“Her word isn’t very good. ... She refused to come,” said Lassart, calling the woman “unstable” and “deceitful.”

Without the woman there to testify, Brown had to decide whether her statements to a 911 dispatcher, hospital physician’s assistant and police detectives could be admitted into court.

Brown ruled the 911 call and conversation with hospital workers were allowed, but statements made to officers were not because she didn’t make them until a month and 19 days after the alleged attack and because she went to police as she was filing a restraining order against Chahal, and as the probation revocation proceedings were starting.

Threat accusations

Prosecutors accused Chahal, his bodyguard and others of threatening to report the girlfriend for purportedly getting a sham marriage in order to obtain a U.S. visa if she went to police about the alleged abuse. Brown said she was troubled by the actions, but didn’t think it was their fault the woman failed to come to court.

Chahal, once called one of America’s most eligible bachelors, sat stoically in court as Brown read her ruling. Kenney asked the judge to immediately put Chahal in jail without bail, which she declined.

Chahal and his attorney left the court without speaking to reporters.

Beverly Upton, executive director of the San Francisco Domestic Violence Consortium, who has been closely following the case, saw the Friday ruling as a win for survivors of abuse.

“We hope the cycle will be broken here with some accountability and raising his awareness that his behavior is harmful,” she said. “It appears that when he feels or thinks that there is some kind of infidelity, he cannot manage his response. And it seems to be that he feels it’s his right to do that.”

Kimberly Veklerov is a San Francisco Chronicle staff writer. Email: kveklerov@sfchronicle.com Twitter: @kveklerov