US President Barack Obama was travelling Sunday to Colorado to visit survivors of the cinema shooting spree, as details emerged about the alleged gunman in the rampage in which 12 people were slain and 58 wounded, dpa reported
Fox News reported that suspect James Holmes had been rejected for membership at a local gun club just weeks before the harrowing attack, after the club's owner perceived "something weird" in a voice message left by the 24-year-old.
As a member of the Lead Valley Range gun club, Holmes could have received weapons training that might have helped prevent a jam in the semi-automatic rifle that was the most powerful of the four weapons he used in the assault, possibly saving dozens of lives. Obama's visit was set to begin a day after police explosives experts neutralized booby traps and bombs in Holmes's apartment.
Law enforcement officials said that the complex series of devices in the third-floor flat was designed to kill anyone who entered, another indication of the calculated mindset of the neuroscience graduate student who is to be charged Monday in the slayings in Aurura, Colorado.
"We believe we have eliminated the major threats there, but we still have some more work to do," said Aurora police chief Dan Oates.
There is no question the apartment was "designed to kill whoever entered it," and most likely that would have been a police officer, he said.
Oates said that Holmes appeared to have amassed the armoury he used in the attack and to booby trap his apartment through large mail order deliveries over recent months.
"What we are seeing here is evidence of some calculation and deliberation," he said.
Police were still collecting evidence in the shopping mall cinema where the attack took place. Eleven of those wounded in the assault remain in critical condition, officials said at a news conference.
Holmes allegedly launched his devastating attack shortly after midnight on Friday as Batman fans packed into a local cineplex to see the eagerly awaited The Dark Knight Rises, which had been expected to have one of the biggest opening weekends of all time.
Wearing a ballistic helmet, a gas mask and body armour, Holmes is said to have detonated two canisters of possible teargas in the crowded theatre before spraying the audience with gunfire from an assault rifle, shotgun and two handguns he had bought legally in recent weeks. Many eyewitnesses said that they first thought the gunshots were part of the movie or were fireworks.
Holmes surrendered without resistance to police in the parking lot of the theatre, within 90 seconds of the first emergency call being received, Oates said.
The harrowing incident has resparked a debate in the US over tighter firearms regulation, strongly opposed by the Republican Party and the pro-gun rights National Rifle Association, one of the country's strongest lobbying organizations.