WASHINGTON — The deadly shooting at a movie theater in Colorado has briefly silenced the presidential campaign, prompting both President Barack Obama and likely Republican challenger Mitt Romney to cut short their schedules and pull advertising in the state out of respect for the victims and their families.

Obama said Saturday in his weekly radio and Internet address that he hopes everyone takes time this weekend “for prayer and reflection — for the victims of this terrible tragedy, for the people who knew them and loved them, for those who are still struggling to recover.”

The president said Americans should also think about “all the victims of the less publicized acts of violence that plague our communities on a daily basis. Let us keep all these Americans in our prayers.”

Aides said Obama received updates Saturday from his homeland security adviser, John Brennan, on the investigation into the shooting and the attempts by authorities to gain access to the suspect’s apparently booby-trapped apartment.

Obama and Romney used campaign appearances on Friday to focus attention on the need for national unity in the aftermath of the shooting in Aurora, which killed 12 people and wounded dozens of others. Their campaign teams rescheduled Sunday show appearances by top aides and surrogates, essentially providing a break in what has been an increasingly testy campaign.

The rampage injected a new tone into the campaign after Obama and Romney had clashed repeatedly over the economy, Medicare and tax returns.   

Obama was set to start his second day of events in Florida when the shooting occurred, prompting his team to address the violence at a previously scheduled rally in Fort Myers, Fla., and scrapping an event in suburban Orlando. Obama told supporters in Fort Myers that the shooting served as a “reminder that life is very fragile.”

“Our time here is limited and it is precious. And what matters at the end of the day is not the small things, it’s not the trivial things,” he said. “Ultimately, it’s how we choose to treat one another and how we love one another.”

Romney echoed Obama’s call for unity, saying at a previously scheduled event in Bow, N.H., that he joined with the president and first lady in offering condolences for those “whose lives were shattered in a few moments, a few moments of evil in Colorado.”

“The answer is that we can come together. We will show our fellow citizens the good heart of the America we know and love,” Romney said.

Other prominent lawmakers called the shooting a time for unity. House Speaker John Boehner, R-Ohio, said in the Republican address Saturday that lawmakers joined Obama in offering condolences and prayers to the loved ones of those who were killed and wounded.

“I know that when confronted with evil we cannot comprehend, Americans pull together and embrace our national family more tightly,” Boehner said.

Yet, beyond the calls for a higher purpose, the shooting could raise the profile of gun rights in the presidential campaign, an issue which has played a minor role so far.

As a senator Obama voted to leave gun makers and dealers open to civil lawsuits, and as an Illinois state lawmaker he supported a ban on all forms of semiautomatic weapons and tighter state restrictions generally on firearms.

Following the killing of six people and wounding of then-Rep. Gabrielle Giffords in Tucson, Ariz., in 2011, Obama called for a series of steps to “keep those irresponsible, law-breaking few from getting their hands on a gun in the first place.”

Among those steps was a better federal background check system. The administration said Friday that it has indeed improved the amount and quality of information poured into that system, allowing background checks to be more thorough.

But the administration has offered no detailed, public explanation of how it is following up on all of Obama’s previous promises, and it had no comment about any need for new legislation.

“The president believes that we need to take common-sense measures that protect Second Amendment rights of Americans, while ensuring that those who should not have guns under existing law do not get them,” said White House press secretary Jay Carney.

Romney backed some gun control measures when he was governor of Massachusetts. When he challenged Sen. Edward M. Kennedy in 1994 he declared, “I don’t line up with the NRA.” In April, Romney told the National Rifle Association he was a guardian of the Second Amendment.

Romney spokeswoman Andrea Saul said the Republican candidate believes that the “best way to prevent gun violence is to vigorously enforce our laws.”

New York Mayor Michael Bloomberg, in a radio interview, urged the president and his challenger to address gun violence forcefully.

“You know, soothing words are nice,” Bloomberg said, “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.”