Cash App founder Bob Lee was a frequent participant in underground sex and drug parties for San Francisco’s tech world elite before he was stabbed to death on a city street — allegedly by the brother a woman who was also a participant in those debauched gatherings called “The Lifestyle.”

Lee and tech consultant Nima Momeni allegedly got into an argument about Momeni’s sister, Khazar Elyassnia — married to a prominent plastic surgeon — in the hours before the stabbing and visited her apartment just before the fatal incident, as CrimeOnline previously reported. Momeni asked Lee if he had been “doing drugs or anything inappropriate” with his sister, which Lee denied.

But multiple people — friends of both Lee, 43, and Elyassnia, 37, told the Wall Street Journal that the pair had been sleeping together as well has participating in “The Lifestyle.”

One friend of Lee’s, Devon Meyers, said the swinging parties helped his friend “unwind” and connect with other people. The parties, Meyers said, had strict rules and anyone who was too “drunk or handsy” would be kicked out.

Sources told the Wall Street Journal that Lee slept with multiple women at the parties, including Momeni’s sister.

The San Francisco Office of the Chief Medical Examiner’s office said in its autopsy report that Lee had cocaine and ketamine in his system when he died.

Lee and Momeni were seen on surveillance video leaving Elyassnia’s apartment and getting into Momeni’s car at about 2 a.m. on April 4. According to court documents, Momeni drove “to a dark a secluded area” on Main Street, where Momeni is accused of stabbing the tech entrepreneur three times and leaving. Police found Lee bleeding “uncontrollably” from “wounds to his chest and hip” when they arrived just after 2:30 a.m. He was taken to San Francisco General Hospital, where he died.

Momeni was arrested on April 13 and charged with murder. His attorney says he will plead not guilty.

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[Featured image: Bob Lee/Twitter]