President Donald Trump on Saturday encouraged a revival of the death penalty while condemning the deadly mass shooting at a Pittsburgh synagogue allegedly carried out by an anti-Semitic gunman.

“When you have crimes like this, whether it’s one, or another one on another group, we have to bring back the death penalty,” Trump said, speaking at a rally in Murphysboro, Illinois.

“They have to pay the ultimate price,” he added. “They can’t do this. They can’t do this to our country. We must draw a line in the sand and say, ‘Never again.’”

The president called for stronger death penalty laws earlier Saturday before another speech at the Future Farmers of America Convention in Indiana.

“When people do this, they should get the death penalty,” Trump said. “Anybody that does a thing like this to innocent people that are in temple or in church ― we’ve had so many incidents with churches ― they should be suffering the ultimate price.”

...This evil Anti-Semitic attack is an assault on humanity. It will take all of us working together to extract the poison of Anti-Semitism from our world. We must unite to conquer hate. — Donald J. Trump (@realDonaldTrump) October 27, 2018

Suspected gunman Robert Bowers, 46, is accused of opening fire inside of the crowded Tree of Life synagogue in Pittsburgh, Pennsylvania, on Saturday morning, killing at least 11 people and injuring six others. Officials said Bowers announced his presence to the congregation by shouting, “All Jews must die,” before the attack.

Bowers, who reportedly had an “assault rifle” and at least three handguns, was later arrested on the third floor of the building after exchanging fire with police. The shooting is considered one of the deadliest attacks on Jewish people in recent U.S. history.

Trump strongly condemned anti-Semitism early in his speech during Saturday’s rally, calling the shooting a “monstrous killing of Jewish Americans.”

“This evil anti-Semitic attack is an assault on all of us. It’s an assault on humanity,” Trump said. “It will require all of us working together to extract the hateful poison of anti-Semitism from our world.”

Saturday’s deadly mass shooting follows the arrest of Cesar Sayoc, 56, a Trump supporter who is suspected of mailing out explosive devices to people Trump opposes. Sayoc’s alleged targets included prominent Democrats such as the Clintons, the Obamas, Democrats in Congress, and CNN’s New York headquarters.

Speaking at a North Carolina rally on Thursday, Trump blamed the media’s negative coverage of him for the heightened political tension in the U.S. The president also urged Democrats and the media to be more civil, ignoring his most recent rallies, in which he encouraged violence against journalists and promoted fear-mongering against immigrants.

Trump supported the death penalty long before his political career. In 1989, the real estate mogul took out full-page newspaper ads urging lawmakers to “bring back the death penalty” in response to a group known as the Central Park Five who were wrongly convicted of attacking a female jogger.

While Trump called for the “ultimate” punishment for Saturday’s suspected gunman, the question of whether the death penalty deters people from committing murder is still up for debate.

At least 20 states have either abolished or overturned the death penalty, according to the nonprofit Death Penalty Information Center. Earlier this month Washington state’s Supreme Court declared capital punishment unconstitutional.

A 2012 scientific review, partially funded by the Justice Department, said there was not enough research that proves the death penalty affects homicide rates and deters the crime.