After a gunman killed 11 people in a Pittsburgh synagogue, Donald Trump condemned the attack and expressed shock at “unimaginable” violence against Jewish people.

Pittsburgh shooting: husband and wife and two brothers among 11 victims Read more

“This was an antisemitic act,” said the president, whose daughter Ivanka and son-in-law Jared Kushner are Jewish. “You wouldn’t think this would be possible in this day and age, but we just don’t seem to learn from the past.”

The president’s words were well received but his comments about whether the attack could have been prevented and his decision to proceed with scheduled political events on Saturday did not go down as well.

Adam Schiff, a Democratic congressman from California, told CNN’s State of the Union: “The problem is not how he’s handling the aftermath, although I certainly don’t agree with his suggestion that this could have been avoided or mitigated if they’d had someone armed in the synagogue. That’s not the answer.

“The broader issue is what kind of climate are we creating in the country.”

The Pittsburgh attack came a day after a man in Florida was arrested and charged with mailing bombs to more than a dozen of the president’s prominent critics, and three days after a gunman in Kentucky tried and failed to get inside a black church, then killed two black shoppers in a nearby grocery store. A witness told a local newspaper the gunman told him: “Whites don’t shoot whites.”

The tone that he sets is one of division, often one of hatred, sometimes one of incitement of violence Adam Schiff

Schiff, who is Jewish, said Trump’s public remarks, appearances at rallies and use of Twitter meant “the tone that he sets is one of division, often one of hatred, sometimes one of incitement of violence against journalists. There’s no escaping the tone that he sets for the country.”

Later on Sunday, Trump duly used Twitter to call the billionaire Tom Steyer, who campaigns for Trump’s impeachment, “a crazed and stumbling lunatic”.

On Saturday, Trump’s response to the attack evolved throughout the day. He tweeted, spoke to reporters and included prefaced remarks to an event in Indiana with a pre-written statement.

The president said he would not cancel a planned rally in Illinois because “you can’t let these evil people change your life, change your schedules, change anything”. He also said his choice to continue was inspired by the reopening of the New York stock exchange after the September 11 terrorist attacks, which he said repeatedly happened the day after the attacks. In fact, it did not.

In his address to a meeting of young farmers in Indianapolis, Trump joked about perhaps cancelling events because he was having a bad hair day – not because of the Pittsburgh attack.

In a brief conversation with reporters after he landed in Murphysboro, Illinois, Trump said he would “have a very much different tone tonight”. At the rally, he duly joked about the Massachusetts senator Elizabeth Warren and listened as the crowd greeted mention of Hillary Clinton with a chant of: “Lock her up!”

“Honestly,” Schiff said on Sunday, “I think this president’s whole modus operandi is to divide us. He gets up in the morning with new and inventive ways to divide us. It’s not enough that on the day of a tragedy he says the right words if every other day of the year he’s saying things to bring us into conflict with each other.”

The Anti-Defamation League said the Pittsburgh shooting was probably the “deadliest attack on the Jewish community in the history of the United States”. On Sunday its chief executive, Jonathan Greenblatt, told NBC’s Meet the Press that Trump had been wrong to say the attack should not have been thought possible.

“We are living in a moment where antisemitism is almost becoming normalized,” Greenblatt said. “And that should shock and move all of us to act.”

The Pittsburgh attack came 14 months after white supremacists marched through Charlottesville, Virginia, carrying torches and chanting “Jews will not replace us”. Trump’s response to fatal violence there, which he blamed on “both sides”, was widely condemned.

On Saturday, he was unequivocal: antisemitic was a “hate-filled poison”, he said, adding: “The widespread persecution of Jews represents one off the ugliest and darkest features of human history. There must be no tolerance for antisemitism in America or for any form of religious or racial hatred or prejudice.”

Pittsburgh shooting: suspect railed against Jews and Muslims on site used by 'alt-right' Read more

He also described the personal toll of America’s increasingly deadly sequence of mass shootings.

“As president, as bad as you felt before, you feel worse,” he said.

But when asked by a reporter what he could do “to end this kind of violence”, he did not have new proposals to make. “The world is a violent world,” he said. He called the alleged gunman, whose social-media profile mentioned Charlottesville and showed a deep familiarity with white nationalist groups – he also criticised Trump – “a mad man” and “a wacko”.

“I think one thing we should do is we should stiffen up our laws in terms of the death penalty,” the president said.

He also acknowledged that debate over gun laws was “a dispute that will always exist”. On Sunday Pittsburgh’s mayor, Bill Peduto, told NBC his city was firmly on one side of that dispute.

“I don’t think that the answer to this problem is solved by having our synagogues, mosques and churches filled with armed guards or our schools filled with armed guards,” Peduto said.

Peduto is part of Mayors Against Illegal Guns, a branch of Everytown for Gun Safety, the largest gun control advocacy group in the US.

“We should try to stop irrational behavior from happening at the forefront, and not try to create laws around irrational behavior to continue,” he argued.