‘I saw the blood trail. I walked it’: Inside the investigation into Bob Lee’s killing

The prosecution rested its case in the murder trial of Nima Momeni, accused of killing tech executive Bob Lee, after a week that included the presentation of DNA evidence and gruesome details about Lee’s autopsy. But the most consequential two days of testimony came from the lead police investigator, Sergeant Brent Dittmer, who detailed how the San Francisco Police Department conducted its investigation. Most of his account hadn’t been heard before. 

On the stand, Dittmer walked the court through the 10 days of the investigation, starting with a blood-spattered sidewalk and ending with the arrest of Momeni.

“A homicide investigation is like putting a puzzle together, but you don’t know how many pieces there are, and some are disappearing,” he said.

What Dittmer did not know on the morning of April 4, but would eventually piece together, was that Lee had been on a two-day drug binge with Khazar Momeni, the defendant’s sister and a central player in the plot of a story that has yet to end in a verdict. Dittmer would surmise that an alleged sexual assault of Khazar by Lee’s friend and alleged drug dealer Jeremy Boivin motivated Momeni to kill Lee. 

What followed, argue prosecutors, was an angry exchange between Momeni and Lee, which appeared to indicate Momeni was angry with Lee for allowing his sister to be assaulted by Boivin. That exchange, plus a number of other pieces of evidence, prosecutors say, led to Momeni fatally stabbing Lee three times — once in the heart — with a knife he retrieved from his sister’s home. 

Under the Bay Bridge on the morning of April 4, Dittmer surveyed the crime scene as officers and the CSI team roamed the blocked-off street. A fresh blood trail from Lee’s wound dotted the sidewalk. One cop stood inside a fenced Caltrans yard near a knife Dittmer was told could be the murder weapon. Crime scene investigator Rosalyn Check and her unit had marked off with small yellow cones potential evidence. And Dittmer’s two-man team began filling him in on what they had found so far. 

Dittmer was told that hours earlier, the first officers on the scene tried to resuscitate a bleeding Lee. In short order, two essential pieces of evidence were found: a potential murder weapon and Lee’s phone, from which he made a 911 call. 

On that call, Lee had said only that someone had stabbed him, not who.

Still moving slowly after a vacation, Dittmer retraced Lee’s final steps. “I saw the blood trail. I walked it,” he said, describing the spatter up Main Street, past bloody handprints on a building and blood smeared on the call box in front of an apartment building.

Within hours, the media found out about Lee’s killing and wild theories of crazed homeless killers began to spread. Elon Musk wrote on Twitter that “violent crime in SF is horrific.”

For Dittmer, a tall, broad man with cropped brown hair and a smile that can turn into an almost imperceptible smirk, the media circus only made his job harder. The investigation would be one of the more than 30 homicides Dittmer has investigated in his six and a half years in homicide, and it was certainly the highest-profile. 

“From the first day, it was clear this was a unique case from the media interest,” he said. “I was trying to control what information was coming out.”

Dittmer feared something about the as-yet-unknown suspect would get out and the suspect would try to evade prosecution.

As reporters flocked to the scene, some even following Dittmer’s video canvasser, Dittmer kept his head down. 

By 10 a.m., Dittmer was at the 1 Hotel, several blocks away. 

He had already spoken to a friend of Lee’s, Ali Ehren, who told him that Lee was visiting from Miami and staying at a hotel near the Ferry Building. Several friends thought Lee had been arrested, as his phone — now in evidence — was at a police station.

Dittmer spoke with the manager of the hotel, who confirmed Lee had been staying there, and then asked that he keep the room untouched as he contacted the on-call warrant judge. Dittmer needed to search the room, get video and records. It would be the first of more than 20 warrants he wrote that week.

Several hours later, Dittmer and his team, along with the same crime scene investigators from under the bridge, entered Lee’s hotel room. Glasses and empty liquor bottles sat alongside baggies of what looked like cocaine. They took photos, collected DNA samples, and bagged up a number of items for testing.

That afternoon, Dittmer got a call that would give him one of his first breaks in the case. It was a man named Borzoyeh Mohazabbi, a DJ and techie friend of Lee’s. Mohazabbi said he’d spent much of the night of April 3 with Lee. Dittmer asked him to come to the homicide unit in the Hall of Justice the next day. 

It wasn’t until nearly 7 p.m. on April 4 that Dittmer spoke to a member of Lee’s family: his ex-wife Krista Lee, who lives in Marin County. She said Lee was in town from Miami for a couple days on business and to see family. 

“As a homicide investigator, you speak with the family. You want to color in the details of that person’s life. Their habits. What they were doing around the time of their death,” Dittmer said on the stand. “Beyond that, there’s a relationship you develop with the family that is very important. There are demands we put on them during this process. We ask them not to say things. You want to get off on the right foot with the family.”

Krista would also tell him that Boivin had said to her that he had a confrontation with Momeni in Khazar’s home, but that he eventually left on April 3 on relatively good terms. 

Dittmer would also interview Boivin, reassuring him that the police had no interest in arresting him for drug offenses. “I’m not the drug police,” Dittmer said he told Boivin. Boivin told him that he and Momeni had had a tense interaction on the night of April 3, after Khazar had alleged Boivin sexually assaulted her. But video collected by police showed him leaving the Millennium Tower alone.

Another night passed and Dittmer still had no suspect. Videos from the scene hadn’t been reviewed, and DNA from the knife hadn’t been processed.

Just after 2 p.m. on the afternoon of April 5, Mohazabbi sat down with Dittmer.

Mohazabbi, a handsome dark-haired man in his late 30s, was uncomfortable talking to police, said Dittmer. Still, Mohazabbi said he had been with Lee for much of the night before his death. Crucially, he said he’d heard Lee take a call in his hotel room from a man he did not know named Nima Momeni.

That same day, police got their first lead about a potential suspect. Officer Rashidian recovered video from Millennium Tower of Lee and Momeni leaving together in a white BMW just before the killing.

In the following days, Dittmer and his team began to focus on Momeni as they pieced together what had happened. They had a “person of interest,” said Dittmer, who began backgrounding Momeni and tasked Sgt. David Goff to surveil him. 

Police needed to match Momeni with the man they had in the video leaving the Millennium Tower with Lee. They also just wanted to see what Momeni was up to. “In my experience, people will lead you to places where evidence can be concealed,” he said.

Dittmer got warrants for GPS tracking devices that Goff wanted to put on Momeni’s Jeep and BMW. He sent a warrant to BMW’s headquarters, requesting that the company send him the location of the car. The company complied and gave him the Mill Valley home address of Mahnaz Tayarani, Momeni’s mother. But by the time police arrived, the car was gone. Eventually the car turned up at a BMW dealership in San Francisco — Momeni’s mother and sister Khazar had sold it back to the dealership.

Dittmer sent the Department of Homeland Security a request to let him know if Momeni tried to leave the country. (Momeni was born in Iran.) He also got a warrant to track Momeni’s phone. 

On April 10, Sgt. Goff followed Momeni to the Burlingame offices of his soon-to-be attorney Paula Canny. In the parking lot, he videotaped Momeni seemingly acting out a stabbing with Canny’s investigator Brian Hedley.

Meanwhile, more video evidence kept rolling in: from 1 Hotel, from the private club the Battery (where Lee and Mohazabbi had been that night), and from the murder scene. In footage from a doorbell camera, images of a white car under the bridge and two figures. 

“It’s grainy, whether you zoom in or not. We’re talking about pixelated blobs. You can’t make out arms and legs. You can’t make out heads. You can’t make out faces,” Dittmer said.

By then, DNA had also come back from the handle of the knife; it wasn’t Lee’s, and it hadn’t gotten a hit when run through a national database. They’d need to match it with a suspect.

Still, Dittmer was getting close. They had video showing Momeni and Lee leaving the Millennium Tower and video indicating the pair had gotten into a fight at the scene of the crime. They also had texts and a witness that appeared to show that Momeni had a motive. Eventually, they would match Momeni’s DNA to what they took from the murder weapon’s handle. 

On the morning of April 13, police fanned out across the Bay Area in a multicounty effort in San Francisco and Alameda. SFPD’s swat team and investigators crossed the bridge to arrest Momeni at his Emeryville home. Dittmer headed to Khazar’s house. 

“I very much wanted to speak to her,” he said. “Her involvement had been brought up in numerous ways by witnesses. I wanted a statement from her about what had happened.”

He did briefly speak with Khazar, but he never got a statement. 

Across the bay, police found four burner phones in Momeni’s home, all of which had been activated after Lee’s death. Eventually, data from those phones and others were collected, revealing text messages between Lee, Momeni, Khazar, and Boivin. Those exchanges would tell the convoluted but now-familiar story of the night of the killing — drugs, arguments, an alleged assault. 

Momeni was officially charged with murder on April 14.