Matt Lambert's Moldy Penthouse Standoff: What Drove the Deadly Rampage?

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The wealthy doctor who opened fire inside a Washington, DC, gym barricaded himself in his mold-filled penthouse for nearly an hour — and called a neighbor to gripe — before ultimately killing himself in a standoff with cops, according to a federal law enforcement source.

During the tense and bizarre confrontation, emergency room doctor Matt Lambert, 55, holed up in his $1.1 million abode shortly after killing at least one person and injuring four in the ground-floor gym of his trendy Logan Circle building.