President Barack Obama speaks about the massacre at a Orlando nightclub during a news conference at the White House in Washington, Sunday, June 12, 2016. AP

Donald Trump seized on the worst shooting in U.S. history to call for a more muscular response to Islamic terrorism – and later noted he’d been congratulated "for being right." Hillary Clinton called it an “act of terror” and called for more curbs on guns.

The two responses illustrated the starkly different approaches the two presumptive presidential nominees could take to governing.

Trump, who has made combating Islamic terrorism a centerpiece of his campaign, tweeted Sunday that he was "praying for the victims & their families” of the Orlando massacre that left 50 dead. But he also added: “When will this stop? When will we get tough, smart & vigilant?"

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The presumptive Republican presidential nominee, who has proposed a temporary ban on Muslim immigration – sparked a backlash with a later tweet: "Appreciate the congrats for being right on radical Islamic terrorism, I don’t want congrats, I want toughness & vigilance. We must be smart!"

Trump called for President Barack Obama – who spoke from the White House – to denounce the overnight shooting as the result of religious terrorism. The shooter, who was felled by police bullets, was identified as Omar Mateen, 29, who was born in the U.S. and is of Afghan descent.

"Is President Obama going to finally mention the words radical Islamic terrorism?" Trump tweeted before Obama spoke. " If he doesn't he should immediately resign in disgrace!"

Obama called the assault an "act of terror and an act of hate," but said investigators had reached "no definitive judgment" for the killer’s motive.

Trump has reacted to past shootings in a similar vein and declared in March that his response to the terrorist attacks in Paris and in San Bernardino had changed the tone of the presidential campaign, and helped him clear the field of his presidential rivals.

“We need protection in our country and that’s going to happen,” he said, noting that after the Paris attacks, “the poll numbers shot up.”

Trump said in a statement that he’ll deliver a speech on Monday on the attack, immigration, and national security, calling the shooter “the son of an immigrant from Afghanistan who openly published his support for the Afghanistani Taliban” and accusing his likely Democratic rival, Hillary Clinton, of wanting to “dramatically increase admissions from the Middle East.”

Clinton, the presumptive Democratic presidential nominee, initially reacted with characteristic caution Sunday, saying on Twitter that her thoughts were with those affected by the "horrific act" as she waited for more information.

Later, after Obama spoke, Clinton’s campaign issued a lengthy statement calling the shooting an "act of terror."

She said the United States needs to "redouble our efforts to defend our country from threats at home and abroad" while calling for additional restrictions on guns, something she has called for repeatedly on the campaign trail.

"We need to keep guns like the ones used last night out of the hands of terrorists or other violent criminals," Clinton said. "This is the deadliest mass shooting in the history of the United States and it reminds us once more that weapons of war have no place on our streets.”

She and President Obama, who endorsed Clinton last week, postponed their first joint campaign event which had been scheduled for Wednesday in Wisconsin.

Sen. Bernie Sanders, who is expected to drop his bid for the Democratic nomination this week, also said that the United States should do more to keep guns out of hands of criminals and the mentally ill. But he reserved judgment on whether it "was an act of terrorism, a terrible hate crime against gay people or the act of a very sick person." 

Research has shown that voters are inclined to give Republican candidates higher marks on terrorist attacks, said Joseph Young, a professor at the School of Public Affairs at American University who studies political violence.

But he said Trump's focus on the Islamic State is “too simplistic” for the Orlando attack, which targeted gays and lesbians.

New Mexico Gov. Gary Johnson, who is headlining the Libertarian Party ticket, called for letting the investigation play out: “We must allow the authorities to do their jobs, understand how this attack came about, and then respond accordingly,” he said in a statement. “It is not a time to either politicize or jump to conclusions.”

This story was originally published June 12, 2016 6:20 PM.