Donald Trump experienced a grim rite of the American presidency on Monday, delivering solemn remarks in the aftermath of a mass shooting in Las Vegas that's now the deadliest in modern U.S. history, leaving at least 59 dead and more than 500 wounded.

Praise for the president's words quickly followed.

"Pitch perfect," CNN's John King remarked immediately after his five-minute statement.

"Presidential," multiple journalists tweeted.

But another way to describe the president's scripted remarks was just that — scripted.

Presidential historians and former White House communications staffers agree the more significant measure of Trump's ability as "consoler-in-chief" won't come from his performance behind a lectern, but from revealing, unscripted human moments in the face of tragedy.

Trump: 'An act of pure evil'1:12

They're the kinds of moments that betray emotion, spurring Barack Obama to sing Amazing Grace after the church massacre in Charleston, S.C., in 2015, or prompting George W. Bush to climb the rubble at the World Trade Center after the Sept. 11 attacks and grab a bullhorn to declare to Americans: "I can hear you, the rest of the world hears you."

Obama eulogizes Charleston shooting victim Rev. Pinckney and leads mourners in singing Amazing Grace2:50

Trump arrives in Puerto Rico on Tuesday, where his ability to express empathy with the 3.4 million Americans impacted there by Hurricane Maria will be scrutinized. His travel schedule now includes a stop in Nevada to console people stunned by a sudden act of indiscriminate mass murder.

David Kusnet, Bill Clinton's former chief speechwriter, said Trump's ability to help the nation deal with tragedy will be defined by what happens when the Teleprompters are gone and his Twitter impulses are unleashed.

"We're talking about the difference between Teleprompted Trump and Twitter Trump," Kusnet said. "We expect the president to speak in ways that heal, that unify and that inspire us to move forward."

Americans want reassurance and empathy in times like these, Kusnet said, particularly as the nation struggles to understand why this massacre happened.

On Sunday night, a gunman sprayed hundreds of rounds of automatic gunfire at people attending an open-air country music concert on the Las Vegas Strip. Police say the 64-year-old shooter, Stephen Paddock, who was perched on the 32nd floor of a hotel across the street, eventually killed himself.

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People tend to the wounded outside the Route 91 Harvest country music festival grounds in Las Vegas.

In his speech the next morning, Trump condemned the shooting as "an act of pure evil." He drew upon the familiar themes that served his predecessors, reciting from scripture and speaking of unity, of grief, and of the country's unbreakable spirit in the wake of tragedy.

He sent a single restrained tweet in the morning, offering condolences to the victims and their families.

"Our unity cannot be shattered by evil. Our bonds cannot be broken by violence," Trump said in his prepared speech. "And though we feel such great anger at the senseless murder of our fellow citizens, it is our love that defines us today — and always will, forever."

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Trump delivers a statement on the mass shooting in Las Vegas in front of a portrait of the country's first president, George Washington. (Kevin Lamarque/Reuters)

Former White House staffers in the Clinton and Reagan administrations all said they could imagine those words being expressed by any of the recent presidents.

"As is often true with his prepared remarks, Trump spoke as a president should," Kusnet said.

'More dissonance'

The problem for Trump, and for the country, Kusnet said, is what the president might later say off-the-cuff. Too often, he said, what Trump recites in speeches is later undermined by unrestrained musings either on Twitter or during news conferences.

Kusnet points to Trump's tweeted criticisms last week of the mayor of San Juan, Puerto Rico, in which Trump accused officials there of wanting "everything to be done for them" after the entire U.S. island territory was decimated by Hurricane Maria and the mayor appealed for speedier help from the federal government.

In August, after the violent white nationalist-led rally in Charlottesville, Va., resulted in the death of a counter-protester, Trump repeatedly declared that blame was deserved on "both sides" of the clashes.

Presidential historian Mike Purdy criticized the president's response to Hurricane Harvey in Texas because Trump struck an awkward tone when he said he saw "a lot of happiness" among Houston's flood-devastated families.

"With this president," he said, "there's more dissonance on what's scripted and what's unscripted, and it's like you can only find out who the real Donald Trump is when you hear him either speak or tweet off-the-cuff."

He said Trump must overcome "emotional blindness" if he's to tap into the kind of empathy that Clinton showed with his "I feel your pain" comment to an activist protesting the government's neglect of the AIDS epidemic in 1992.

"Quite frankly, anybody can read a speech," Purdy said. "What will be interesting to see is how that plays out when [Trump] visits Las Vegas."

'Don't know yet what's in his heart'

Given the death toll and reports that Paddock had at least 17 guns in his hotel room and 18 guns at his home near Las Vegas, what was left unsaid in Trump's prepared remarks could also be revealing, said Mark Updegrove, author of The Last Republicans: Inside the Extraordinary Relationship Between George H.W. Bush and George W. Bush.

Despite declaring himself a defender of the Second Amendment during the 2016 campaign, Trump might still have used the tragedy to call for stricter gun-control measures — if that's what he actually wants.

"If there's any chance of enacting meaningful gun control, it could best come out of the ashes of a tragedy of this magnitude," Updegrove said.

But Trump's visit to Vegas on Wednesday may be more revealing, he said, as the president has the opportunity to connect with grieving Americans impacted by the 273rd mass shooting this year.

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U.S. President George W. Bush addresses a crowd as he stands with retired firefighter Bob Beckwith, right, from Ladder 117 at the scene of the World Trade Center attacks in New York on Sept. 14, 2001. (Reuters)

Updegrove recalls that moment in 2001 when Bush climbed the heap of ruin in New York City and took the bullhorn at Ground Zero as a particularly clarifying one.

"He rallied the nation, and we saw his heart."

It's in those organic moments, he said, when people see a president's empathy and moral clarity. 

It's been more difficult for Updegrove to figure out Trump, who's been wildly unpredictable when he goes off-script.

"We don't know yet what's in his heart."