Updated 12:53 p.m. - The shooting of moviegoers in Colorado “reminds us all of the ways that we are united as one American family,” President Barack Obama said Friday in remarks mourning the victims of the overnight massacre.

Speaking in Florida, where he cut short a campaign trip, the president led a crowd in a moment of silence and called for Americans to reflect on what he called a senseless act of violence.

“Even as we learn how this happened and who's responsible, we may never understand what leads anybody to terrorize their fellow human beings like this,” Obama said. “If there's anything to take away from this tragedy it's the reminder that life is very fragile. Our time here is limited and precious.”

Mitt Romney, speaking early Friday afternoon in New Hampshire, said: "Our hearts break with the sadness of this unspeakable tragedy. Ann and I join the president and first lady -- and all Americans -- in offering our deepest condolences to those whose lives were shattered in a few moments of evil in Colorado."

The presidential campaign was essentially put on hold after a gunman waged an assault on viewers of a midnight showing of “The Dark Knight Rises” in Aurora, east of Denver.

Slideshow: Shooting at Batman screening in Aurora, Colo.

Obama canceled a planned campaign stop for later Friday in Florida to return to the White House; Vice President Joe Biden and first lady Michelle Obama also canceled political events set for Friday afternoon. The Romney campaign canceled a planned series of radio interviews this afternoon.

“I am so moved by your support, but there are going to be other days for politics. This, I think, is a day for prayer and reflection,” the president told supporters.

Additionally, the both the Romney and Obama campaigns put a hold on airing political ads on television on Colorado for at least the weekend.

"I stand before you today not as a man running for office, but as a father and grandfather, a husband and an American," Romney said, also striking an apolitical tone in his statement. "This is a time for each of us to look into our hearts and remember how much we love one another and how much we love and how much we care for our great country."

Details from the shooting were still emerging as of late Friday morning, but White House press secretary Jay Carney said that the president was first notified of the shooting at 5:26 a.m. ET by John Brennan, his homeland security adviser. Obama called the mayor of Aurora later in the morning, and received a follow-up briefing from Brennan, White House chief of staff Jack Lew, and FBI Director Robert Mueller.

"The president orders that his administration do everything that it can to support the people of Aurora in this extraordinarily difficult time,” Carney said in a gaggle aboard Air Force One.

Mandel Ngan / AFP - Getty Images

President Barack Obama steps off Air Force One upon arrival at Southwest Florida International Airport July 20, 2012 in Fort Myers, Florida.

Most political reaction revolved around expressing sympathies for the victims of the shooting.

"I am stunned and furious at the news of the shooting at the Aurora Century 16 Movie theatre this morning,” said Democratic Colorado Rep. Ed Perlmutter, whose district includes the site of the crime. “Colorado is not a violent place, but we have some violent people. We are a strong and resilient community, and we will lean on each other in the days, weeks and months to come.”

Few elected officials touched on the impact of the Colorado shootings on the long-simmering debate about gun control laws.

"I would say as you know the president believes we need to take common sense measures that protect the Second Amendment rights of Americans while ensuring that those who should not have guns under existing laws do not get them," Carney said when asked about the impact of the shooting on the gun debate. "We're making progress in that regard in terms of improving the volume and quality of information on background checks, but I have nothing additional on that for you. This is obviously a recent event."

One of the few exceptions to that came from New York City Mayor Michael Bloomberg, a longtime advocate for stricter gun laws.

"You know, soothing words are nice, but maybe it's time that the two people who want to be president of the United States stand up and tell us what they are going to do about it, because this is obviously a problem across the country," Bloomberg said on WOR Radio in New York. "No matter where you stand on the Second Amendment, no matter where you stand on guns, we have a right to hear from both of them concretely, not just in generalities -- specifically, what are they going to do about guns?"