Social media account linked to DC shooter complained of disrepair, invoked man who killed healthcare CEO

The shooter who opened fire in a gymnasium At a luxury apartment building in Washington, D.C., on Thursday morning, he was complaining about mold and water problems in his apartment before his deadly attack on the building manager, police said.

One person was killed and four others injured in the shooting in the Logan Circle neighborhood. Police identified the deceased victim as James Stuart, 46, who managed the building.

Police said the shooter, identified as Dr. Matt Lambert, 55, continued shooting in the street and then killed himself in his apartment after a standoff. Three firearms were recovered from his apartment, according to police sources in Washington.

An account on X under the name @OfMiceandMold served as a repository for complaints about the alleged disrepair of the apartment where Lambert lived.

In dozens of X-rated messages, he expressed his frustration with Metropole Condominiums’ construction contractors, EJF Real Estate Services, and his allegations that they failed to resolve his unit’s problems. CBS News has contacted EJF Real Estate Services for comment.

Lambert, who ran a Washington-based health care consulting firm, purchased the condo in September 2016 for $1,095,000, according to Washington tax records. Court documents show he owned a penthouse in the building.

Before the shooting, he released what he claimed was a technical report investigating mold and water problems in his building. “My manifesto is an engineering report,” he writes.

At one point he appeared to summon Luigi Mangionethat took down UnitedHealthcare CEO Brian Thompson in 2024. On October 1, he wrote, “After months of ‘Luigi’ (delay, deny, defend) tactics from the HOA, we were finally able to submit an independent engineering report into the docket,” and said he would share the engineering report on X “when the time is right.” Mangione had “delay, deny, defend” written on the bullets he used in the shooting.

In an April social media post, he wrote: “If you’re looking for the property manager, I’d check out the gym.”

Lambert sued the Metropole Condominium Association, listing his grievances and alleging damages of more than $290,000 in May.

The Metropole condominium association and EJF denied causing the damage and said any damage was caused by third parties beyond their control and that Lambert had failed to limit its losses.

The Metropole Condominium Association and the EJF did not immediately respond to requests for comment.

Police said he fired shots inside the Vida Fitness Center on the ground floor of the building, which serves the building’s residents.

A woman said she was on a treadmill in the gym when a man right next to her was shot and killed.

“There was no way to get out of the gym other than through that stage,” she said.

“It was like chaos. It was horrible, honestly.”

A witness who was about 20 feet from the shooting told CBS News he lived directly below Lambert and described him as becoming increasingly upset during HOA meetings. He said Lambert had a habit of inviting people to his apartment to show them how serious the situation was. The witness called the building a “tight-knit community” with 99 units.

The witness said that during the shooting and confrontation with police, his girlfriend barricaded herself in the apartment. He said he is now underwater since responding to a fire that broke out when police say the shooter cut a natural gas line leading to his chimney.

Logan Circle is a vibrant neighborhood in Washington, DC, gentrified in the 2010s, with historic architecture and some of the city’s most popular restaurants and bars.

Lambert was the founder and CEO of MLEM, a healthcare and technology consulting firm, according to his LinkedIn profile. He earned his undergraduate and medical degrees at Marshall University in West Virginia and completed his residency at West Virginia University, according to his profile.