Doctor kills building manager in Washington DC after long mould dispute, police say

On Thursday morning, a fire alarm went off inside an apartment building in Washington DC's Logan Circle neighbourhood, about a mile north of the White House. Within minutes, residents were running for cover as gunfire broke out. By the end, the building's manager, 46-year-old James Stuart, was dead, four other people had been taken to hospital, and the man police say was responsible had died of a self-inflicted gunshot wound.

Police identified the suspect as Matt Wade Lambert, a 55-year-old doctor who lived in the building. According to investigators, the shooting began inside a gym in the building, where Stuart was pronounced dead at the scene. Lambert then left the gym and, police believe, fired from the patio balcony of his seventh-floor apartment at four people on the ground level. One of those four is in critical condition. Police said it was not immediately clear whether Lambert had any relationship with them.

Lambert then barricaded himself inside his apartment. Jefferey Carroll, interim chief of the Metropolitan Police Department, told a news conference that he fired through the door at officers at least twice. Negotiators were on the phone with him when they heard a gunshot and he stopped responding. Officers forced their way in and found what appeared to be a self-inflicted gunshot wound.

Carroll said police believe the attack grew out of a long-running dispute. "We do know that there has been an ongoing dispute between the suspect in this case and the building, condo, homeowners association management regarding maintenance issues, mould and the like," he said, adding that Lambert had filed a civil case against them. Investigators are still working on the exact timeline, his motive and other details.

The scene in the apartment suggested preparation. Officers recovered three firearms, all of which Lambert used on Thursday. Police said none were registered to him in Washington DC, and it is unclear how he obtained them. He also had containers of flammable liquid inside the apartment. Carroll said police suspect an accelerant was used, though they do not know whether it was gasoline or something else, and believe there was probably some pouring. "It does appear there was some level of planning associated with this," he said.

Residents and gym users described confusion and fear. Jonathan Csapo, a BBC producer who lives in the building, said the fire alarm sounded and then, as he came out of a fire escape, he heard gunshots very close by. "I could see the smoke, I could see the flash. We just all started running," he said. He and others took cover behind a small brick structure near the building before a building manager led him back inside to a safe room. "And then everybody started screaming," he said.

Michael Carney told the Washington Sun he was on a treadmill at the Vida Fitness gym when he heard "one pop", which he took for an exercise ball bursting. Then he saw a shot victim on the floor. People hid behind planters, he said, and someone pulled a fire alarm. Outside, he heard five or 10 more shots that seemed to come from a nearby alley. Another witness told the paper she thought something had crashed or fallen, and did not realise it was a gunshot until later. Mayor Muriel Bowser called it a "senseless act of gun violence" and said the White House had been briefed.

The legal fight had gone on for more than a year, according to the Washington Sun, between Lambert and both the Metropole Condominium Association and the building's property manager. He told a reporter from the paper, who was then working with another outlet, that renovations in the building had caused severe water leaks and black mould that left his million-dollar penthouse unliveable. "It's affected every part of my life - my sleep, dietary habits," he reportedly said in December.

His former lawyer in the civil case, Joel Braithewaite, told NBC News that the dispute and the upkeep of the home had cost Lambert $300,000 (£227,000). He said Lambert regarded the apartment as "his prized possession", reported mould and water problems soon after moving in, and spent thousands on mitigation. Braithewaite said his client felt wronged and believed the condo association took no ownership of the problems. Investigators are still establishing the full sequence of events, and one of the wounded remains in critical condition.