Presumptive GOP nominee Donald Trump's first tweet was a fairly measured comment about the deadly mass shooting in an Orlando gay nightclub.

"Really bad shooting in Orlando. Police investigating possible terrorism. Many people dead and wounded."

His second tweet, an hour and a half later, was a return to campaign trail politics - an attempt to falsely recast a verbal attack he made against a disabled journalist.

Then came another, more sympathetic tweet about the Orlando tragedy, followed by one in which he took credit for "being right on radical Islamic terrorism".


And then Trump went fully on the attack, saying, "Is President Obama going to finally mention the words radical Islamic terrorism? If he doesn't he should immediately resign in disgrace!"

Trump's approach to the deadliest mass shooting in US history posed a sharp contrast to the conventional one of presumptive Democratic nominee Hillary Clinton.

She first tweeted a note of concern for the victims; hours later, she issued a statement that sought to address the main issues that the tragedy touched on - terrorism, gay rights and gun control.

The disparity between the two encapsulates the choice facing voters this November: Do they see Trump's bombast as the solution to a dangerous world, or do they find comfort in Clinton's more familiar manner?

Trump's way served him well in the Republican primaries. His standing improved after the shootings in San Bernadino, California, and his call for "a total and complete ban" on all Muslims entering the United States.

But it is unclear whether the much larger general-election audience will react as favourably to a candidate who has called for "a hell of a lot worse" than waterboarding, has said of terrorists that "you have to take out their families" and who is willing to circulate unconfirmed reports on social media amid a federal investigation.

At one point, Trump, who has nearly 9 million followers, tweeted, "Reporting that Orlando killer shouted "Allah hu Akbar!" as he slaughtered clubgoers".

This appeared to be a slightly altered version of a tweet sent by a Fox News contributor, which did not cite a source for the information.

The Mayor of Orlando says there were 50 casualties and there are 53 more hospitalized after a mass shooting at a popular gay nightclub. Source: AP

Stuart Stevens, who served as Mitt Romney's chief strategist during the 2012 campaign, called Trump's statements and actions on Sunday "childish".

"Every day he finds a different way to show he's unqualified to be president," Stevens said. "Today he's accepting congratulations at a time when 50 people are slaughtered."

Jennifer Palmieri, communications director for the Clinton campaign, said in a statement, "This act of terror is the largest mass shooting in American history and a tragedy that requires a serious response. . . . Donald Trump put out political attacks, weak platitudes and self-congratulations. Trump has offered no real plans to keep our nation safe and no outreach to the Americans targeted, just insults and attacks."

Trump's handling of the unfolding events - private consultation with aides while issuing a flurry of proclamations and comments on social media - is reflective of how he often handles breaking news. While he works closely with advisers to craft the theme of public remarks and statements, he believes it is also crucial for him to be part of the national conversation as soon as possible.

"He'll monitor everything, that's how he is. It's not just on Twitter but on his smartphone and television and articles," Sam Nunberg, a former Trump aide, said when asked how Trump digests major news events.

Former House speaker Newt Gingrich, a Trump ally, said in an interview that the mogul should "ignore" the rush of critics who cast Trump's responses as inappropriate.

"What Trump ought to do, and what he has historically done, is go to the country. And he should take the elite media head-on. There is no possibility of coexisting peacefully with these people. They are his mortal enemy, so he should relax and accept it," Gingrich said. "He should use a campaign on social media to beat them."

The first openly-gay elected official in Orlando responded to the mass shooting at a gay nightclub saying, "if you think that you're going to stab at the heart of us by doing this horrible, violent act you're not because we love." Source: AP

Clinton began with a personally signed tweet that drew no conclusions about the incident. "Woke up to hear the devastating news from FL. As we wait for more information, my thoughts are with those affected by this horrific act."

Hours later, she issued a statement calling on the United States "to redouble our efforts to defend our country from threats at home and abroad" while also imposing restrictions on firearms and ensuring that gay, lesbian, bisexual and transgender Americans are not targeted because of their sexual orientation or gender identity.

Clinton has made gun control and gay rights central issues in her campaign. Following a mass shooting last year in Roseburg, Oregon, she issued a detailed plan to expand gun background checks through executive action: President Barack Obama later adopted a similar approach. She has called for the reinstatement of an assault weapons ban, favours a California proposal regulating ammunition and has promised to seek legislation ending the immunity gun manufacturers have from some lawsuits.

And while Clinton lagged behind many Democrats in calling for the legalisation of same-sex marriage, she has repeatedly called for ending discrimination against members of the LGBT community during her presidential campaign.

The mass shooting prompted both leading presidential candidates to tear up their campaign schedules. Trump had planned to give remarks tomorrow at the New Hampshire Institute of Politics at St Anselm's College focused on scandals linked to Hillary Clinton over the years, but the speech has been reframed to "further address this terrorist attack, immigration, and national security."

Trump, who has told aides he sees the issues as interconnected, said, "I am trying to save lives and prevent the next terrorist attack. We can't afford to be politically correct anymore".

Clinton had been scheduled to deliver a speech in Cleveland tomorrow, followed by one in Pittsburgh on Wednesday, two events aimed at refocusing her campaign on Trump now that she has amassed enough delegates to secure her party's nomination. She cancelled a much-heralded joint rally with Obama slated for Thursday in Green Bay, Wisconsin, citing the attack.

The President framed the shooting as a moment when the nation needed to come together to support those who had been victimised and defend America's traditions of diversity and tolerance.

He did not mention proposals to ban Muslims from entering the country or religious tests designed to prevent Muslim refugees from Iraq and Syria from coming to the United States. But they were clearly on his mind as he called on Americans not to "give into fear or turn against each other".

Obama described the attack as "a sobering reminder that attacks on any American - regardless of race, ethnicity, religion or sexual orientation - is an attack on all of us and on the fundamental values of equality and dignity that define us as a country."

And he made a point of saying the Orlando nightclub where the killing occurred "was a place of solidarity and empowerment," where members of the city's gay, lesbian, bisexual and transgender community "came together to be with friends, to dance and to sing and to live".

It is unclear whether the more nuanced approach Clinton and Obama are advocating - one that calls on Americans to refrain from targeting people from the Mideast or of Middle Eastern descent while pursuing incremental gains against Islamic extremists overseas - will resonate with the majority of voters.

For Trump, according to Ronald Reagan's former education secretary William Bennett, tomorrow's speech represents "a test" of whether he can rise above the infighting that dominated the GOP's nomination contest.

"If he looks and sounds big, he can put his detractors to rest - the Mitt Romney people and the others who have been going after him," said Bennett, who has grown friendly with Trump.

"It's a time for him to say we're at war and get the whole country and party behind him. This is the kind of event that can cut through the rhetoric and the name-calling about him pretty quick and make it all fade into the background."