A suspected gunman who burst into a Pittsburgh synagogue shouting "All Jews must die!," killing 11 worshippers and wounding six other people, was charged late Saturday with 29 federal counts, including hate crimes.

Robert Bowers, 46, was taken into custody after being wounded in a shootout with police at the scene of the "horrific" mass shooting, according to law enforcement officials. Among the wounded were four police officers.

Bowers allegedly burst into the Tree of Life Congregation Synagogue in the Squirrel Hill neighborhood of Pittsburgh and screamed anti-Semitic epithets, as he opened fire on the congregants, law enforcement officials said.

Police said he was armed with an assault rifle and three handguns.

The official who is not authorized to comment publicly said the suspect left an alleged trail of anti-Semitic rants on social media accounts, prompting authorities to designate the FBI as the lead agency to investigate the attack as an alleged hate crime.

"It’s a very horrific crime scene," Pittsburgh Public Safety Director Wendell Hissrich said at a news conference. "It's one of the worst I’ve seen."

Attorney General Jeff Sessions said Bowers could face the death penalty.

“These alleged crimes are reprehensible and utterly repugnant to the values of this nation," Sessions said in a statement. "Accordingly, the Department of Justice will file hate crimes and other criminal charges against the defendant, including charges that could lead to the death penalty.

The call of a shooting at the synagogue came in at around 9:54 a.m., he said. Armed with an assault rifle and four handguns, Bowers allegedly shot and killed the 11 victims before being confronted by police.

Pittsburgh police officers confronted Bowers as he allegedly tried to exit the synagogue, said Pittsburgh bureau FBI Special Agent in Charge Bob Jones. A gunfight erupted and two officers were injured, he said.

Bowers retreated back into the synagogue as SWAT members descended onto the scene. After another exchange of gunfire, two SWAT members were wounded and Bowers was taken into custody, Jones said.

Bowers was in fair condition with multiple gunshot wounds, authorities said. Investigators believe he acted alone.

"This is the most horrific crime scene I've seen in my 20 years with the FBI," Jones said.

The names of the victims were not expected to be released until Sunday.

Teams of armed police swarmed the neighborhood near downtown Pittsburgh just before 10 a.m. Saturday. Residents were urged to shelter in place as armed law enforcement agents canvassed the neighborhood.

Speaking to reporters at Andrews Air Force Base in Maryland, President Donald Trump praised law enforcement's response in the shooting and called the suspect in custody a "madman" and a "whacko."

He said he would like to see more armed guards at synagogues and other places of worship and impose more death penalty sentences on convicted murderers.

"It's a terrible, terrible thing what's going on with hate in our country and, frankly, all over the world," Trump said. "Something has to be done."

Posts believed to be from Bowers’ social media accounts show pictures of several Glock pistols in their cases and derogatory remarks about refugees, Jewish people and Trump. In his last post on the social network Gab, issued Saturday morning, Bowers criticized a refugee advocacy group who "likes to bring invaders in that kill our people."

"I can't sit by and watch my people get slaughtered," he wrote. "Screw your optics, I'm going in."

More:Shooting at Tree of Life Synagogue: Politicians, local leaders react to tragedy

More:What we know about the shooting at Tree of Life Synagogue in Pittsburgh

Squirrel Hill is a Jewish enclave near Carnegie Mellon University. A little more than 50 percent of Greater Pittsburgh’s Jewish community lives in or around the neighborhood, said Jeff Finkelstein, president and CEO of the Jewish Federation of Greater Pittsburgh.

Tree of Life immediate past president Michael Eisenberg told KDKA-TV that there were three congregations meeting simultaneously, probably totaling around 100 people, at the time of the shooting. They were gathered in the main part of the building, as well in the basement and in the rabbi study room, he said.

The shooting occurred during a baby-naming service. Eisenberg said he spoke with a maintenance man who hid in one of the bathrooms during the shooting and witnessed a shot congregant before fleeing through an exit.

Eisenberg said he was on his way to service there when he noticed police swarming the streets.

"There were police cars everywhere, guns drawn, rifles," he told KDKA-TV. "It was surreal."

In the interview, Eisenberg said synagogue officials recently adjusted the exit doors to make them easier to open, which probably saved lives on Saturday. During Saturday services, the front door is kept unlocked, allowing visitors to come and go freely, he told KDKA-TV.

Security has always been a concern at the synagogue but the shooting will force officials to rethink their threat-prevention measures, Eisenberg said.

"This will be a catalyst for increased security in the future," he told the station.

More:Trump says Pittsburgh shooting has 'little' to do with gun laws, armed guard could have prevented tragedy

The synagogue was founded 150 years ago and offers members a "traditional Conservative service with a modern sense of family" and shabbat service on 9:45 a.m. Saturdays, according to the Tree of Life's website.

Calling it an act of "horrendous anti-Semitic brutality," Israeli Prime Minister Benjamin Netanyahu said in a statement that "I was heartbroken and appalled by the murderous attack on a Pittsburgh synagogue" and that all Israelis "grieve with the families of the dead."

Vice President Mike Pence commented on the incident while at an event with Nevada Republicans in Las Vegas, scene of last year's deadly shooting that left 58 people dead.

"As Las Vegas knows all too well, what happened in Pittsburgh today is not just criminal, it's evil," he said. "There's no place in America for violence or anti-Semitism."

Contributing: Kevin Johnson