US doctor kills building manager after long-running dispute over mould, police say

A doctor who had been in an ongoing dispute over mould and other issues at his Washington DC apartment fatally shot his building's manager and fired at four others before killing himself, police say.

Building manager James Stuart, 46, was pronounced dead at the scene, while four others were rushed to local hospitals for treatment.

The shooting began on Thursday morning local time inside a gym in an apartment building in the Logan Circle neighbourhood, which is about a mile (1.6km) north of the White House.

Police said the suspect, identified as 55-year-old doctor Matt Wade Lambert, then barricaded himself in an apartment, and later died of a self-inflicted gunshot wound.

While the suspect was barricaded, "he did fire through the door at officers at least on two occasions", Jefferey Carroll, the interim chief of the Metropolitan Police Department, said at a news conference.

Negotiators had been on the phone with the suspect when they heard a gunshot and he stopped communicating with them, according to Carroll.

Officers forced their way into the apartment and saw the suspect had what appeared to be a "self-inflicted gunshot wound", he said.

Authorities are still working to understand the exact timeline, suspect's motivation, and other details of the incident.

"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," Carroll said.

"That there was a civil case that he filed against them. So we believe that it's related to that."

Police believe that after Lambert opened fire inside the gym, he fled the scene and then shot at the four other victims, who were on the ground level, from his patio balcony area on the building's seventh floor.

One of the injured is in a critical condition, police said.

It was not immediately clear whether he had a relationship with the other victims.

Authorities recovered three firearms from Lambert's apartment,all of which he used in Thursday's incident.

"It does appear there was some level of planning associated with this," Carroll said.

It was unclear how he obtained the weapons, as he did not have any firearms registered to him in Washington DC, police said.

Lambert also had containers of flammable liquid inside his apartment.

"We do suspect that there was probably some level of accelerant. We don't know if it was gasoline or something else," Carroll said. "So we do believe there probably was some level of pouring there."

A BBC producer who lives in the building where the shooting happened, Jonathan Csapo, said a fire alarm went off. 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. That was our first instinct," Csapo said.

"We immediately ran and took cover behind a barricade, a little brick structure just near the building."

Csapo said he was then taken back inside to a safe room by a building manager.

"And then everybody started screaming," he said.

Michael Carney told the Washington Sun he was on a treadmill at the Vida Fitness gym when the shooting started.

He said he had heard "one pop", which he assumed was an exercise ball bursting, before seeing a victim on the floor who had been shot.

"Everyone was kind of just hiding behind planters and stuff," he said, adding a fire alarm was pulled.

Once outside the gym, Carney said he heard five or 10 shots that seemed to be coming from a nearby alley.

Another witness told the Washington Sun that she heard "an enormous, loud thing" in the fitness centre and more shots outside the gym after being evacuated.

"I thought something had crashed or fallen," she said. "I didn't know it was a gunshot until later."

Washington DC Mayor Muriel Bowser called it a "senseless act of gun violence" and said the White House had been briefed.

Lambert had been locked in a bitter legal dispute with the Metropole Condominium Association and the building's property manager for more than a year, according to the Washington Sun.

He told the newspaper's reporter, who was then working with another media outlet, that his million-dollar penthouse had been rendered unliveable after building renovations led to severe water leaks and black mould.

"It's affected every part of my life - my sleep, dietary habits," Lambert reportedly said in December.

"I pride myself on my resilience, and I've been kind of surprised at how much it has been affected."

Lambert's former lawyer, Joel Braithewaite, who represented him in the civil case against the building's management, told NBC News that the legal dispute and home maintenance cost his client $300,000 (£227,000).

Braithewaite said his client considered the DC apartment "his prized possession". But soon after moving in, he reported mould and water issues, and spent thousands on mould mitigation, according to the civil case.

He said his client felt wronged and as though the condo association took no ownership for the issues he had with the unit.