At least a dozen people were killed and 58 injured during a shooting spree at a mall movie theater in Aurora, Colo., police authorities said.
The suspected gunman has been identified as former medical student James Holmes. The 24-year-old was taken into custody Friday after releasing a gas canister and opening fire into the multiplex theater at about 12:30 a.m. MDT. Authorities have not yet indicated a motive.
The massacre took place during a midnight showing of the latest Batman movie, "The Dark Knight Rises." The incident is being called one of the deadliest shooting sprees in history.
"Witnesses tell us he released some sort of canister. They heard a hissing sound and some gas emerged and the gunman opened fire," Aurora Police Chief Dan Oates said at a news conference.
"There were bullet (casings) just falling on my head. They were burning my forehead," Jennifer Seeger recalled.
"Every few seconds it was just boom, boom, boom," she said. "He would reload and shoot and anyone who would try to leave would just get killed."
Police later found the suspect near a car behind the movie theater.
"A gas mask, rifle, handgun, at least one additional weapon (were) found inside," Aurora police spokesman Frank Fania said.
Not far from the theater, FBI agents and police used a hook and ladder to reach Holmes' apartment. They evacuated five other nearby buildings after discovering that the unit was booby trapped.
Jessica Ghawi, a 24-year-old aspiring sportscaster, died in Friday's shooting. Amazingly, she had narrowly missed another shooting in a Toronto food court last month.
"I was shown how fragile life was on Saturday," Ghawi had described of the Toronto shooting in her blog. "I was reminded that we don't know when or where our time on Earth will end, when or where we will breathe our last breath."
For many families and friends of the victims, it's been a day of waiting and not knowing whether loved ones were dead or alive.
On the ground, members of the Billy Graham Rapid Response Team ministered to those waiting for news.
"They're in shock, they're challenged," response team member Chaplain Dowling said. "They're very, very emotional. They're very talkative, trying to process what they've seen."
Meanwhile, President Barack Obama said he was "shocked and saddened" by Friday's tragedy and is pledging his support to the victims' families.
Speaking at what was originally scheduled as a campaign event at Fort Myers in Florida, the president opted to set politics aside in light of the tragedy.
The massacre, he said, served as a "reminder that life is very fragile."
"Our time here is limited and it is precious," Obama said. "And what matters at the end of day is not the small things, it's not the trivial things which so often consume us and our daily lives. Ultimately it's how we choose to treat one another and how we love one another."
In a statement released earlier, the president vowed that his administration would "do everything that we can to support the people of Aurora in this extraordinarily difficult time."
"We are committed to bringing whoever was responsible to justice, ensuring the safety of our people, and caring for those who have been wounded," he said.
GOP presumptive nominee Mitt Romney also offered his condolences, calling the massacre an act of "senseless violence."
"We are praying for the families and loved ones of the victims during this time of deep shock and immense grief," he said.