SAN FRANCISCO (KRON) -- Defense attorneys for Bob Lee's accused killer, Nima Momeni, admitted in opening statements that Momeni stabbed the tech mogul under San Francisco's Bay Bridge. According to defense attorney Saam Zangeneh, Lee pulled out the kitchen knife and Momeni fought back in self-defense. Prosecutors say Lee was unarmed and Momeni stabbed him in the heart April 4, 2023 because he was enraged about Lee's "inappropriate" relationship with Momeni's younger sister, Khazar. The Cash App founder and his friend, Bo Mohazzabi, allegedly left Khazar at a drug dealer's apartment, where she was given "date rape" drug GHB, Zangeneh said. Khazar, center, arrives for the arraignment of Nima Momeni, her brother, at the Hall of Justice in San Francisco, Thursday, May 18, 2023. (AP Photo /Godofredo A. Vásquez) Mohazzabi testified on the stand Tuesday afternoon. He testified that he left the apartment with Lee and went to Lee's room at Hotel 1, where they talked about new tech business ideas. The hotel room was littered with empty alcohol bottles and cocaine, according to testimony. For the jury to reach a guilty verdict for first-degree murder, prosecutors have to prove at trial that the slaying was premeditated. Rick Lee, father of Bob Lee (left), and Krista Lee, ex-wife of Bob Lee, walk with Bob Lee's children into the courtroom on October 14, 2024. (Photo by Lea Suzuki /San Francisco Chronicle via Getty Images) A mountain of clear surveillance video footage recorded Momeni and Lee leaving Khazar's apartment at Millennium Tower around 2 a.m. They appear to be cordial as Momeni opens his BMW passenger side door for Lee to get in. They drive off together. Lee called 911 just 30 minutes later, begging a dispatcher for help as he bled to death on Main Street. Jury hears Bob Lee’s last words on 911 tape According to opening statements delivered this week, questions that will likely remain unanswered for the jury are: What were Momeni and Lee talking about as they sat in the BMW together for five minutes outside Millennium Tower, and for 12 minutes under the Bay Bridge? Grainy surveillance video shows two figures stepping out of the white BMW and talking on Main Street for five more minutes before Lee was fatally stabbed. What was their conversation about? Assistant District Attorney Omid Talai told jurors, "We can't answer every question." Bob Lee According to Talai, evidence and testimony at trial will prove Lee's death was a premediated murder, and the motive centers on Khazar. Momeni stole a knife from Khazar's kitchen and hid it under his clothing, prosecutors said. Assistant District Attorney Omid Talai told jurors, "The defendant does not drive Bob home (to 1 Hotel). He takes him here on the 400 block of Main Street. Bob ends of dying about a block away. Ladies and gentlemen, you are sitting in court with a murderer. A coward who stabbed an unarmed man three times." Because words exchanged inside the BMW are unknown, both prosecutors and defense attorneys are leaning heavily on text messages and phone calls exchanged between Khazar, Lee, and Momeni from the day before the homicide and the hours after Lee's death. Mohazzabi overheard Momeni call Lee around 9 p.m. on April 3 demanding to know what happened to his sister at the drug dealer's apartment. Khazar was "disheveled" and distraught when Momeni picked her up from the apartment, Zangeneh said. Khazar arrives for the arraignment of Nima Momeni, her brother, at the Hall of Justice in San Francisco on May 18, 2023. (AP Photo/Godofredo A. Vásquez) Talai said the phone call was "aggressive, awkward, (and) strange. It's not a conversation, it's an interrogation. Our wannabe tough guy big brother is convinced something happened." Mohazzabi could hear the entire phone conversation because Lee had put the call on speaker. "Bo says 'this is absurd, he's crazy, get off the f**king phone with the guy,'" Talai told the jury. Khazar is slated give highly-anticipated testimony. She showed up at the courthouse on Tuesday, but as of Wednesday afternoon, she has yet to appear on the witness stand. Defense attorneys are seeking to ban Lee's ex-wife from the courtroom while Khazar testifies. They claim that Krista Lee attempted to intimidate Momeni's sister because she did not cooperate with police. Jurors viewed text messages exchanged between Momeni and his sister hours after Lee was killed and before Khazar knew he died. CSI detective testifies about Bob Lee’s blood trail In one text Momeni wrote, "I don't know what Bob ended up doing at the bar or strip club. Started preparing for the rape case against both of them. Let's talk when you are calm and we can coordinate plans with an attorney. Hope you can make better decisions. Start thinking about your place in the world." Khazar replied by writing, "Rape case? Nima you're f**king psychotic at times." Talai reminded the jury that the texts were exchanged "between two people who have no idea a jury will be looking at it."