Portland police shut down part of Allen Avenue on Friday during a response to an “emergency.” Gregory Rec/Staff Photographer

A police standoff that started before 11 a.m. Friday ended four hours later when police found a person dead on the second floor of a condominium at The Residences on Allen Avenue in Portland.

Police heard a gunshot and believed that the man took his own life, but detectives were processing the scene for evidence Friday and the state medical examiner was expected to determine an exact cause of death.

Portland police said they had contact with the man last month when he was taken into protective custody under Maine’s yellow flag law. Several firearms were confiscated and he was prohibited from having any dangerous weapons.

Police spokesman Brad Nadeau said they didn’t know how or where the subject had since acquired a gun. “That will be part of our investigation going forward,” he said.

The yellow flag law is under intense scrutiny because it was never activated to take weapons away from Robert Card, who shot and killed 18 people at two locations in Lewiston on Oct. 25 before he died from a self-inflicted gunshot wound.

Police are withholding the name of the man who died Friday until family members are notified. There is no indication that anyone else was home around 10:30 a.m. when Gorham detectives knocked on the door to deliver court papers and heard a gunshot.

“It’s an apparent suicide. As best we can tell, he was the only person there at the time,” interim Assistant Police Chief Robert Martin told reporters gathered near the scene soon after the body was discovered.

During the emergency operation, a stretch of Allen Avenue between Washington Avenue and Ray Street was closed to traffic, and residents of the North Deering neighborhood were notified via reverse 911 to shelter in place. Nearby schools were notified but not put in lockdown, although students were advised to avoid the area.

Portland’s special reaction and crisis negotiation teams and a Cumberland County K9 team responded to the 24-unit condo complex at 459 Allen Ave. after Gorham police reported hearing the gunshot. Martin said he didn’t know what paperwork the officers were trying to deliver.

However, on Nov. 26, Portland police had taken the subject into protective custody and secured a weapons restriction on him under the yellow flag law, Nadeau said in a statement. Several firearms were taken from him at that time and he was prohibited from having any weapons, Nadeau said.

On Friday, police first tried to establish phone contact with the man, then tossed two flash-bang devices into the house in an effort to coax him outside, Martin said. Then they used a series of three robots to search the house, one floor at a time.

“We’re trying to get communication as best we can,” Martin told reporters around 1:30 p.m.

Once robots searched and cleared the first floor, a police officer entered the house and tossed a third robot up to the second floor, Martin said. Then K9 Teemo entered the house and located the body, which was captured by the robot’s camera. Martin wouldn’t say in which room the body was found.

The roadblocks and stay-home orders were lifted at 3 p.m.

Janice Murphy, who owns a condo at The Residences, was on a treadmill at the gym Friday morning when she began receiving text messages from neighbors about the standoff. The retiree was unable to return to her home during the emergency action.

Murphy said she lives across from the condo that police entered Friday. The man who lived there was a renter who moved in a little over one year ago, she said.

“He was a quiet person but friendly,” she said. “He was an older person. He would occasionally walk by the house with a cane.”

Murphy said her condo development is typically quiet with mostly retired and professional residents, but she saw police there on a recent weekend near the townhouse where Friday’s shooting occurred.