The gunman in the Washington, DC, gym shooting is a wealthy doctor who had been locked in a battle over black mold in his $1.1 million penthouse — and cited a report about it as his chilling “manifesto.” Dr. Matt Lambert, an emergency room doctor, had sued his homeowners association in March 2025, claiming that scaffolding from repairs on his trendy Logan Circle building led the dangerous fungus to spread. “My manifesto is an engineering report,” an X account linked to Lambert tweeted at 8 a.m. Thursday— minutes before he opened fire inside his building’s ground-floor gym, killing at least...