The White House says U.S. President Barack Obama will travel to Colorado Sunday to visit with victims of Friday's mass shooting rampage and their families.

A White House spokesman announced plans for the trip Saturday night, and said it will include meetings with local officials.  The itinerary was disclosed just hours after President Obama used his weekly radio address to call for national prayer and reflection, as the Denver suburb reels from the tragedy.

Twelve moviegoers were killed and dozens wounded early Friday as a gunman sprayed scores of bullets into a crowded theater.

Earlier Saturday, Aurora Police Chief Dan Oates said bomb squads disarmed a tripwire and detonated a homemade explosive device at the suspect's apartment near Friday's crime scene.  Oates said the apartment was rigged to kill whomever first entered it.  He said in all likelihood that would have been a police officer.

Police identified the suspect as James Holmes, a 24-year-old student whom officials say was preparing to withdraw from a graduate studies program.

The heavily-armed Holmes was arrested just outside the theater right after the bloodbath, in possession of a rifle, a shotgun, two handguns, a gas mask and a bulletproof vest.

Officers then surrounded the young man's apartment building about six kilometers from the crime scene, and evacuated all residents. 

Police said the attacker's motivations remained unclear, nearly two days later.

President Barack Obama and one of the top Republican figures in Congress, House Speaker John Boehner, were among national leaders who have publicly mourned the victims and offered condolences to their families.