The well-heeled Washington, DC doctor who killed his condo manager in the building’s gym vented online about the state of his condo for 14 months — before exploding this week with the crazed mass shooting that also saw four others hit.

Dr. Matt Lambert, 55, started a dedicated X account, “Of Mice and Mold,” in September 2025 to rant about problems with the Logan Circle apartment he bought in 2016 for $1.095 million.

He used the account to regularly rant about his homeowners association – right up until Thursday, when he posted a “manifesto” to justify gunning down building manager James Stuart, 46, and shooting four others at random before turning the gun on himself.

He had already filed a lawsuit against the Metropole Condo Association by the time he created his X account — alleging his home experienced “no significant water intrusion, mold, moldy smells, moisture accumulation, or related damage” prior to the remediation efforts that started in 2023.

The X account remains a timeline for his deadly fixation on conditions he faced in the Metropole building and his hatred of the condo’s management company, EJF Real Estate Services.

The first post on the page is a photo of the building where he had a seventh-floor apartment.

But later that day he then posted about a “mandatory rodent extermination” in the upscale building.

Lambert initially highlighted water damage to walls, moaned about unfinished facade rehabilitation works at the Metropole building, and rodent infestation – seemingly an effort to hurry condo bosses.

Lambert also shared pictures of himself carrying out moisture-reading tests — which came back with the color red, indicating serious dampness.

In April of this year, however, his posts became more chilling – where he directed one resident to the gym to find the building manager after they complained about no hot water, without naming Stuart.