Police today surrounded the apartment of the man suspected of shooting dead at least 12 people and wounding 50 others during a late-night screening of the new Batman movie after he admitted to having explosives stored at his home.

James Holmes, 24, was arrested after entering the mall in Aurora, Colorado dressed in black and wearing a gas mask and bullet-proof vest and opening fire at random.

A San Diego woman, who identified herself as Holmes’ mother, said that her gut instinct told her that her son was responsible for what has become the state’s worst mass shooting since Columbine.

—

Police said Holmes, who lives about four miles from the scene of the shooting in North Aurora, operated on his own. The Defense Department said he has never served in the Army.

He is in police custody and the FBI says there is no indication that incident is tied to any terrorist groups.

He was not any watch list that would have alerted authorities that he was dangerous, officials told NBC.

Police chief Dan Oates said that an apartment block in the north of Aurora had been evacuated as a consequence of the man’s claims he had explosives at his home.

Residents told how they heard a small explosion as a police robot entered the ‘booby-trapped’ apartment.

A law enforcement source told CBS that police saw what looked like ‘buckets of extra ammunition’ and some kind of chemical inside his home.

FBI agents and police used a hook and ladder fire truck to reach inside the building, footage from the scene revealed.