Internet sleuths hunt for clues on murder of UnitedHealth's Brian Thompson

Zooming in on surveillance footage of a gun that could have had a silencer fitted to it. Scouring the web to identify the brand of a backpack. Triangulating data of a rental bike to uncover an escape route.

Wednesday's shocking murder in Manhattan of UnitedHealthcare CEO Brian Thompson — what police called a targeted killing — brought out a bevy of sleuths and true-crime fans across social media looking for clues about the killer's motivation and how he managed to flee from the scene and seemingly disappear into the city of more than 8 million people.

By Thursday, police were examining evidence ranging from surveillance video to items discarded nearby that could contain DNA to find the killer. Authorities also asked for the public's help, releasing a photo with a clear view of his face.

Meanwhile, platforms including Bluesky, Reddit and X sprouted hundreds of posts from amateur gumshoes poring over video and photos. "Dude had a suppressor, which is an extremely difficult thing to acquire, especially in a state like New York," wrote one Reddit user.

Such forums are rife with so-called internet detectives who pick through publicly available reports to uncover information in the aftermath of major crimes. Sometimes, they succeed: Online sleuths helped investigators identify numerous rioters who took part in the US Capitol riot on Jan. 6, 2021, following Joe Biden's presidential election victory in 2020.

But such "crowd-sourced investigations" also can go awry. Following the April 2013 Boston Marathon bombing, Reddit users spread theories that pointed at the wrong people, which were later amplified by publications including the New York Post. The FBI released pictures of their leading suspects to quell the speculation.

Social media helps people connect around a shared subject, but it also blurs the line between news and speculation, said Tahneer Oksman, a professor in Marymount Manhattan College's communications department in New York.

"So many people are no longer making the important distinctions between getting vetted information and chatting/speculating about such vetted information," she said.

SCOURING THE INTERNET
A Reddit post about Thompson on the subreddit MorbidReality, which has more than 1 million members, garnered over 260 comments. Users speculated the killer's weapon was a Station 6 pistol or an "exotic firearm called a B&T VP9." Others focused on the backpack, calling it a "Peak Design Everyday Backpack 30L, Camera Bag."

On X, some users tried to chase leads on Citi Bike - New York's bicycle rental system - for clues. One user posted details about a bike that seemed to have been the only one that left the area shortly after the shooting and headed toward Central Park. Police later told media outlets they believe that the killer likely used an unmarked e-bike, not a Citi Bike.

Early Thursday, users examined another crumb: reports that the words "deny," "defend" and "depose" were carved into the shell casings found at the scene. The words evoke the title of a 2010 book critical of the insurance industry titled "Delay Deny Defend: Why Insurance Companies Don't Pay Claims and What You Can Do About It."

Those comments set off more chatter about the shooter's motivation, ranging from an early 2024 federal investigation into the company to a lawsuit filed by a Florida pension fund alleging insider trading.

Retired FBI agent Jennifer Coffindaffer on Thursday posted a 26-minute video on X laying out thoughts on the murder, saying the killer knew exactly where Thompson would be and when. "That just tells me there likely could be somebody on the inside, somebody that knew when he would be leaving," she said.

Coffindaffer did not respond to attempts to contact her on X or LinkedIn.