PITTSBURGH, Pa. — At least 11 people are dead and six others wounded — including four police officers — after a man walked into a Pittsburgh synagogue shouting "All Jews must die," according to witnesses and local news reports.

Local news station KDKA identified the shooter as Robert Bowers, 48. The suspect, described as a heavy-set, bearded white male, surrendered and was arrested after the horrific incident at The Tree of Life Synagogue in Squirrel Hill, Pittsburgh, Pa., on Saturday morning.

A SWAT team had been reportedly talking with the suspect and he was crawling and injured. The anti-Semitic mass shooting happened during heavily-attended weekly Shabbat services. Police sources told The Washington Examiner that the suspect yelled "All Jews must die" several times as he opened fire.

Police would not confirm the number dead early Saturday afternoon, and said that federal authorities will be taking over the investigation.

NBC News reported that the shooter was armed with an AR-15-style rifle and multiple handguns. Congregants told MSNBC that a circumcision celebration, known as a bris, was taking place in the synagogue.

First reports of an active shooter came at 10:20 a.m. The target was the conservative synagogue in the leafy, tree-lined streets of the historically-Jewish Squirrel Hill neighborhood of the city. Police were said to have received calls from people barricaded inside the synagogue and to have been forced to shelter behind their vehicles as the gun fired at them when they arrived.

Michael Eisenberg, past president of the Tree of Life, described the synagogue's Saturday morning services to KDKA. He said: “At 9:45 there were three simultaneous congregations’ services that were being held.

In the main part of the building, The Tree of Life has a service that has about 40 people in it. Just below that there is a basement area where New Life congregation would have been having their Shabbat service. There would have been 30-40 people. Just adjacent to Tree of Light’s service area, a congregation was in the rabbi study room and they would have had approximately 15 people in there.”

Pittsburgh has experienced mass shootings before. Richard Baumhammers went on a killing spree in April 2000 that left five dead and one person paralyzed. A month earlier, Ronald Taylor shot five people in a McDonald's in nearby Wilkinsburg, Pa., killing one in March 2000.

In 2009, four people were killed at a L.A. Fitness in Collier Township, a Pittsburgh suburb, by Georgie Sodini, and in 2012 at Western Psychiatric Institute, John Shick shot and killed two people and injured seven more.

President Trump weighed in Saturday on Twitter, saying that he was watching the events unfold and warning people in the area to remain sheltered. He said in a subsequent tweet he would address the shootings during a speech already scheduled in Indianapolis later in the day.

Police warned that the area was dangerous in a series of tweets Saturday morning.

“There is an active shooter in the area of WILKINS and Shady,” the Pittsburgh Public Safety Department said in a tweet. “Avoid the area. More info will be released when it is available.”

Officials also asked members of the media to stop calling officers' cell phones as they were responding to the shooting.

Kimberly Leonard is reporting from Washington, D.C.