Cash App founder, Bob Lee, attended underground sex and drug parties with sister of his alleged killer.

Cash App founder Bob Lee attended underground sex and drug parties with sister of his alleged killer.

Lee’s death was initially believed to be a case of random violence in a city where crime is soaring, but his friends suggested it was instead a result of the Cash App founder’s indulgent lifestyle among the upper echelon of Bay Area society where cocaine and swingers were common, the Wall Street Journal reports.

Known in wealthy circles as “The Lifestyle,” Lee, 43,a father of two, allegedly enjoyed the city’s underground party scene, as did Khazar Momeni, wife of a prominent plastic surgeon and sister of Nima Momeni.

Lee was allegedly confronted by Nima about the hard partying and his sister’s involvement in an argument erupting in the early hours of April 4 when Lee was stabbed multiple times, prosecutors said.

Lee reportedly stumbled around begging for help before collapsing near the Bay Bridge — just 16 minutes from Khazar’s apartment.

The two had been sleeping together in the weeks leading up to his death in early April, his friends told the Wall Street Journal, and many feared he had fallen into a dangerous lifestyle, surrounding himself with the wrong group of people.

Prosecutors have previously said Momeni stabbed Lee in the heart multiple times after vowing to 'come down hard on him' and grilling him over his relationship with Khazar, with whom the Cash App founder exchanged intimate text messages.

Friends of the murdered tech mogul have described how the father-of-two took drugs casually and partied regularly.

They said Lee, 43, was passionate about developing the Venmo competitor following his career as a Google programmer.

But to unwind, Lee would allegedly take ketamine and cocaine and travel to raves across the world.

Once, Harper Reed, the CEO of General Calacic Corporation, claimed he and Lee even stripped off their pants to attend a party.

Lee, who was separated from his wife, would often sleep with multiple women at these parties, including Khazar and Nima, sources told the Wall Street Journal.

It was at one of these parties on April 3, when Nima — who sources say was a recluse at these parties, often standing in the corner — confronted Lee.

Prosecutors say Nima asked Lee if he and his sister were 'doing drugs or anything inappropriate.'