Bay Area tech entrepreneur Nima Momeni entered no plea at his first court appearance in the stabbing death of Cash App founder Bob Lee. Police say Momeni knifed Lee in the ribs in the early hours of April 4.
Fox News was in the courtroom Friday morning as Momeni appeared wearing an orange jail sweatshirt and pants, a black coronavirus mask and shackles around his ankles.
He said little, only speaking in response to a question from the judge, saying, "Yes, your honor."
Momeni's sister, Khazar Momeni, and her husband, Dr. Dino Elyassnia, were at the courthouse for the proceedings.
A man with them said the family had no comment when asked how Momeni knew Lee.
Court documents obtained by Fox News Friday revealed that investigators helped piece together the crime by reviewing text messages exchanged between Lee and his suspected killer's sister.
In one conversation, she reportedly told the tech titan that he "handled himself with class" after her brother allegedly "came wayyyyyy down hard" on him.
WATCH: Nima Momeni's relatives decline to comment on how stabbing suspect knew victim Bob Lee
The texts were revealed as part of District Attorney Brooke Jenkins' motion asking the court to keep Momeni behind bars until his next hearing April 25.
"[Momeni] drove [Lee] to a dark and secluded area the opposite direction of his hotel," the filing alleges. "We know through a text message from Defendant's sister to Victim, Defendant was previously upset with Victim and ‘came down hard on’ him."
According to the documents, an unnamed witness told police Lee was drinking with his suspected killer's sister the afternoon before his murder.
"Witness 1 was unsure if Victim and Female had an intimate relationship," the filing states, but it also notes that, "Female was married, but the relationship had possibly been in jeopardy."
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The court filings unveiled Friday also reveal that police recovered the suspected murder weapon, a bloody 4-inch kitchen knife, discarded near the crime scene.
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That evening, the witness told police Momeni was grilling Lee in his hotel room about "whether his sister was doing drugs or anything inappropriate."
Lee tried to assuage Momeni's concerns, the witness said, and left his hotel room after midnight.
When Lee was still gone the following morning, the witness told police that he reached out to the sister, who said Lee visited her that night "for a second."
"She fell asleep and didn't know when he left," the filing states.
Police obtained surveillance video from the residential building showing Lee and Nima Momeni getting into an elevator just after 2 a.m. They got into Momeni's white BMW and drove around the corner.
By 2:30 a.m., Lee appeared on surveillance video nearby, stumbling with stab wounds to his torso. The autopsy found he'd been stabbed three times, once in the hip and twice in the chest, including a wound that pierced his heart.
Police Chief Bill Scott said Thursday three search warrants had been served as part of the investigation, two within the city and a third in Emeryville, across the Bay Bridge, where Momeni lived and worked.
Lee called 911 from the San Francisco side of the bridge around 2:30 a.m. April 4.
Police found him outside the Portside residential tower on Main Street, rendered aid and rushed him to a hospital, but he succumbed to his injuries.
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One of the search warrants was served at a luxury downtown high-rise where Momeni's sister and her plastic surgeon husband own a condo, according to local reporting.
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One was served at Momeni's home in Emeryville, across the Bay Bridge, Scott said Thursday, and one more was served elsewhere in San Francisco.
Records show the sister and her husband purchased a $2.7 million condo in the Millennium building in 2016.
Police served one of the warrants there Thursday, The San Francisco Standard reported, not far from Lee's hotel and where police found him with stab wounds in Rincon Hill April 4.
Police have declined to confirm that claim or provide additional details beyond the allegation that Momeni knew Lee before the attack.
Messages left for the Elyassnias were not immediately returned.
Momeni was arrested in Emeryville, where he lived and had an office for his outsourcing firm, Expand-IT, according to police.
A former employee tells Fox News Digital that Momeni was "the cool guy at times" but could also be "wild and erratic."
Jake Shields, the professional mixed martial artist and a friend of Lee's who has raised concerns about public safety in the city, told Fox News Digital he recognized Momeni and his sister from the same social scene but didn't know much about them.
Momeni is due back in court on April 25. He is expected to be held without bail until then.
Momeni is facing charges of murder and the special allegation that he used a knife for the crime.
He has not yet entered a plea.
Lee, who had lived in San Francisco for about two decades before relocating to Miami, will be laid to rest in his hometown of St. Louis, Fox News Digital has learned.
Fox News' Claudia Cowan and Jasmine Baehr contributed to this report.
