AFP: The alleged gunman behind the Colorado theatre shooting was "relaxed" and compliant when arrested after the massacre which killed 12 people, an officer told a court hearing Monday.         

James Holmes, who was wearing body armour and a mask, told police his name and volunteered that there were improvised explosive devices rigged up in his apartment, when detained after the shooting last July in Aurora, Colorado.         

Holmes, sporting dark brown hair and a full beard, was led into court in handcuffs at the start of a week-long hearing expected to hear more details about the shooting, which revived America's perennial debate over gun control.         

Clad in dark red prison scrubs, Holmes -- who had bright orange hair when he first appeared in court last July -- stared straight ahead and talked to no-one in the courtroom, as relatives of the victims looked on.         

Aurora policeman Jason Oviatt told the court how he at first thought Holmes was another officer when he arrived with dozens of other police, in response to 911 calls about the midnight shooting at a screening of the new Batman film. 

Image: Police photograph of James Holmes | Photograph: Reuters