President Barack Obama cut short his campaigning in Florida to return to the White House on Friday after what he called "horrific and tragic" mass shooting at a Colorado theater.
Both he and Republican challenger Mitt Romney paused in the middle of a tight election race to express their shock
over the deadliest mass shooting in the US since the one on the Virginia Tech campus in 2007.
A gunman opened fire early on Friday at the theater on the opening night of the latest Batman movie. Authorities say at least 12 people were killed and at least 50 were injured.
The FBI said there was no indication that the shooting had any connection to terrorism.
Obama's campaign at first said the president would address the shooting at a campaign rally, then it announced he was cutting short his two-day Florida visit.
Obama said he was "shocked and saddened" by the shooting and urged the nation to "come together as one American family."
Romney said in a statement that he was "deeply saddened by the news of the senseless violence."