Law enforcement sources have identified the gunman in Thursday’s fatal shooting at a Washington, D.C., gym as Dr. Matt Lambert, who reportedly had a long-running dispute with his homeowners association.
Two law enforcement officials and a person familiar with the case confirmed Lambert’s identity to The Associated Press. They spoke on the condition of anonymity because they were not authorized to discuss the investigation publicly.
Police said the shooting began shortly after 8 a.m. inside Vida gym in the Logan Circle neighborhood. One person died, four others were injured and the shooter was killed.

Law enforcement officers respond to an active shooter situation near Washington, D.C.’s Logan Circle Nov. 12, 2026. (Annalise Peatel)
The AP reported that Lambert had been involved in a continuing conflict with the management of his apartment building. He filed a lawsuit against the company last year, according to the report.
The AP also reported that, fewer than 10 minutes before emergency calls about the shooting began, Lambert appeared to post the words “My manifesto is an engineering report” on an X account called “OfMiceandMold.” The post included screenshots from the report.

A cordoned-off area after a shooting in Washington, D.C., Nov. 12, 2026. (Reuters/Aaron Schwartz)
The screenshots described a dispute between Lambert and the Metropole Condominium Association involving alleged “mold” and “water intrusion” problems.

Law enforcement officers work at the site of a shooting in Washington, DC, Nov. 12, 2026. (USA TODAY Network via Reuters Connect)
The account contains a large collection of posts, photographs and videos alleging problems inside the apartment. In an early October post, Lambert accused the HOA of using what he described as “months of ‘Luigi’ tactics” and referred to submitting an “independent engineering report.”
The investigation into the shooting remains ongoing.