Campaigns Cancel Events and Pull Ads

VIDEO: President Obama comments on Colorado movie theater
WATCH Colorado Shooting: Obama Calls for Moment of Silence

With reporting from ABC's Jake Tapper, Mary Bruce and Emily Friedman

President Obama interrupted his campaign schedule today to ask his supporters to think of the victims of this morning's deadly shooting in Colorado, and he promised that the shooter will see justice for his "heinous crime."

The Obama and Romney campaigns canceled rallies and pulled their ads in Colorado after the gunman killed more than a dozen people who were watching the premiere of the new Batman movie, which began showing at midnight.

"We will take every step possible to ensure the safety of all of our people," Obama, who was staying at a hotel outside West Palm Beach, Fla., said at an event that was intended to be a campaign rally. Obama left the event to return to the White House.

Observing about 15 seconds of silence for the victims, Obama told the crowd that the shooting is a reminder that "life is very fragile," and that he and his wife would be hugging their daughters a little tighter today.

"It's what we do on a daily basis to give our lives meaning and to give our lives purpose," he said. "That's what matters. At the end of the day, what we'll remember will be those we loved and what we did for others. That's why we're here."

Counterterrorism adviser John Brennan told Obama of the shooting at 5:26 a.m., the White House said. He has also been briefed by the FBI director and his chief of staff while on the way to the airport in Florida. Obama spoke with Aurora's mayor and Colorado's governor as well.

The White House says he'll meet with key advisers this afternoon in the Oval Office.

The Obama campaign has removed its negative ads targeting Mitt Romney for his time at Bain Capital and his tax records, and Obama's super PAC has suspended advertising in Colorado too. "We have asked affiliates to pull down our contrast advertising for the time being," said campaign spokeswoman Jen Psaki. "It takes time for stations to be able to do this, but we are making every effort."

In his brief speech this morning, Obama said today should be focused on "prayer and reflection," for which he was applauded.

"There are going to be other days for politics," he said. As he ended his speech, his supporters chanted, "Four more years!"

Romney also spoke exclusively about the shooting at an event that had been campaign related.

"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," he said.

Ann Romney canceled an event in Michigan, and the Romney campaign has also pulled its ads in Colorado.

"Today we feel not only a sense of grief but perhaps also of helplessness," he said. "The answer is that we can come together."

The first lady and Vice President Biden also have canceled campaign events today. Michelle Obama was scheduled to be in Virginia, and Biden planned to raise money for Senate Democrats in Texas.

Neither campaign has said whether Obama or Romney plan on visiting Aurora to talk about the shooting. Perhaps Obama's most memorable speech on tragedy was in Tucson, Ariz., after Gabby Giffords was shot in the head and six people died. In that speech, Obama invoked the life of a 9-year-old girl who was killed and said he wanted to live up to her expectations.