SAN FRANCISCO (KRON) -- For the first time since Nima Momeni was charged with murdering tech mogul Bob Lee, the accused killer told his side of the story on Wednesday. Momeni broke his silence in front of San Francisco jurors who will decide his guilt or innocence. Momeni claimed when he made a joke about Lee spending time with strippers instead of his family, Lee "blew up" and attacked with a knife. Lee, 43, was a divorced father of two. Prosecutors said Momeni plotted to murder Lee because he was enraged about Lee's "inappropriate" relationship with Momeni's younger sister, Khazar. Khazar previously testified that she was sexually assaulted by Lee's drug dealer on April 3, 2023, the day before Lee was slain. Momeni was the last person seen with Lee alive as the two men left Khazar's luxury apartment at Millennium Tower together on April 4, 2023. Bob Lee, left, and Khazar, right Nima Momeni testifies in self-defense Wearing a suit and tie on the stand, Momeni described what allegedly happened when Lee was stabbed through the heart under the Bay Bridge and bled to death on Main Street. Momeni testified that after they left the tower, they drove around the city in his BMW while they talked about going to a strip club or bar. Lee huffed whippets that he found in Momeni's car and said he wanted to retrieve more cocaine from his hotel room, according to the defendant. Momeni testified that the mood suddenly changed when he made a "bad joke." Momeni told jurors, "I made a bad joke. I said, 'If it was my last night in town, I'd go hang out with my family instead of f**king around in strip clubs.' It set him off. He just blew up in front of me. He went from zero to one hundred. He was very angry." Nima Momeni, right, testifies in self-defense on Nov. 13, 2024 in San Francisco Superior Court. (Courtroom sketch by Vicki Behringer) Lee moved from the San Francisco Bay Area to Miami a few months before his death. For the first week of April 2023, Lee was staying in a San Francisco hotel and went to several parties, including one at Khazar's apartment and another at Twitter's headquarters. On Tuesday jurors saw a copy of Lee's toxicology report that showed he had cocaine and ketamine in his system. During direct examination on Wednesday, defense attorney Saam Zangeneh asked Momeni if he explained to Lee that the strip club comment was just a joke. Momeni answered, "Yes I did. Everything I said just made it worse. He's yelling, cursing at me, circling around me, getting in my face." In the courtroom, Zangeneh played a Nest surveillance camera's video, the only video that exists of the stabbing. The video is too grainy to see what is happening between two men standing under the Bay Bridge. Zangeneh told Momeni to stand up and act out what is happening in the video. Momeni testified that Lee pulled out a kitchen knife.   On Nov. 13, 2024 in a San Francisco courtroom, Nima Momeni and his defense attorney re-enacted as altercation between Momeni and Bob Lee. (Courtroom sketch by Vicki Behringer) The defense attorney asked, "What was your first reaction when you saw the knife?" Momeni answered, "I was afraid for my life. I just wanted to control his hand. I was grabbing it and pushing him backward. He took a swing." For the re-enactment in front of the jury, Zangeneh pretended to be Lee holding a knife, and swung his arm toward Momeni. Momeni grabbed his defense attorney's arm and re-directed it back toward the attorney's chest.  The defendant said the altercation happened so fast that he had no idea Lee was stabbed and fatally wounded.  "He just turned around and started walking away," he testified.  According to testimony from investigators earlier in the trial, Lee was stabbed three times, including a fatal blow through his heart. Lee left behind a heavy blood trail as he called 911 and desperately tried to find help. Jurors listened to Lee's 911 call and watched surveillance footage of Lee bleeding to death. Bob Lee Momeni testified that he didn't want Lee to get the knife back, so when he saw it on the ground, he grabbed it and threw it over a fence. As he drove away from the crime scene and back to his home in Emeryville, Momeni said he called Khazar. "I told her, 'Bob went crazy, don't let Bob back in (her home). He just went crazy on me and attacked," he told the jury. "Did you know Mr. Lee was fatally injured?" Zangeneh asked. "Absolutely not. He seemed normal as he walked away," Momeni answered. Khazar Momeni walks out of a San Francisco courtroom with her mother after she testified on Oct. 22, 2024. (KRON4 Photo) Bob Lee's brother reacts to testimony While Momeni testified in self-defense, Bob Lee's brother and father listened in the courtroom gallery. The homicide victim's brother, Timothy Lee, said Momeni was lying through his teeth. "It's absolutely insane. Go off on somebody for a joke? It didn't make sense to me. Bob would never pick up a knife. Nima has a history with knives, collected knives ... he is a bully. My brother was a tech guy, he's a sweetheart, there's no hard edge to him," Timothy Lee told reporters outside the courtroom. "There is no doubt about what actually happened. You're all intelligent people here. How do you stab somebody three times, and then think that they are not injured? The little lies that he's dug ... I'm hoping that the jury sees." Timothy Lee scoffed at the defense team's strategy. Momeni's lawyers are being paid for by Khazar and Khazar's wealthy husband, Dino Elyassnia. The victim's brother said, "They have had a long time, 18 months, to come up with something, and this is what they are coming up with? He has a raft of lawyers, he's got five lawyers up there ... they are spending a ridiculous amount of money to defend him, and this is the best that they have? It's not very much." Prosecutor spars with Momeni on cross-examination Momeni had to answer tough questions when Assistant District Attorney Omid Talai launched into his cross-examination. Talai said Momeni's story on the stand was absurd. Bob Lee was an executive for cryptocurrency company MobileCoin and the founder of Cash App. His violent death sent shockwaves through the Bay Area tech industry. Talai said, "You knew Mr. Lee was a prominent, beloved, and respected man in the tech community.  And your story is he wanted to kill you over a dumb joke? Over a dumb joke? This bad joke made Bob Lee go from zero to a hundred, and bring out a knife that he had concealed from you, to kill you on Main Street under the Bay Bridge?" Momeni answered, "I was in fear for my life. He was trying to hurt me." The accused killer and the prosecutor began talking over each other as Momeni in a heated exchange. Talai asked, "Have you looked at all of the evidence in this case?" Momeni answered, "Not every piece of evidence." Talai fired back, "You are on trial for murder, and you have not looked at every piece of evidence?" Momeni replied, "No." The prosecutor asked if Momeni had seen the San Francisco Police Department reports, text message exchanges, and surveillance videos gathered for the case. Momeni answered, "I looked at the false police report accusing me, talking about me chasing him down the street, ridiculous accusations." Talai asked Momeni about text messages that he exchanged with his sister between April 4-5, 2023. "Your sister texts you, 'You're a f**king psychotic,' on the day you happened to kill a man," Talai said. "She calls you a lunatic and a psycho?" Momeni smiled at the prosecutor and responded, "She calls me many things. You should see her in person. She has a fiery attitude." Khazar, who is married to a plastic surgeon, and Bob Lee had a casual romantic relationship. Khazar called Bob Lee "babe" in some flirty messages, and wrote "love you," in others. The jury saw a message from Bob Lee when he asked Khazar for a sexual favor in exchange for a tank of nitrous whippets. Khazar testified that she was high on drugs before and after the homicide. https://twitter.com/AmyLarson25/status/1848767224804479140 On Wednesday, Talai pointed out another text message from Khazar in which she tells her brother that cocaine "messed up" his mind and "the Bob thing hit hard." Momeni testified, "She's mad at me, obviously. I don't know what she's thinking when she's f**ked up on drugs." Before Khazar found out that Bob Lee was dead, she sent an "invaluable text" message on the morning of April 4, 2023, Talai said. Her text to Lee stated, "Just wanted to make sure your doing ok. Cause i know nima came wayyyyyy down hard on you. And thank you for being such a classy man handling it with class." Khazar Momeni ‘can go f**k herself,’ Bob Lee’s ex-wife says In opening statements, Talai described the defendant as "a coward who stabbed an unarmed man three times." On Thursday morning, Momeni will return to the witness stand to resume cross-examination. If convicted, he faces a life prison sentence.