The 24-year-old man accused of killing 12 people in a Colorado movie theatre shooting, dubbed the worst mass shooting in American history, made his first court appearance Monday. He appeared dazed in the prisoner’s box, clad in a burgundy prison jumpsuit, with dyed orange hair.

James Holmes has been held in solitary confinement at Arapahoe County detention centre since Friday. The judge said he’ll be formally charged next Monday. Eighteenth Judicial District Attorney Carol Chambers said her office is considering pushing for the death penalty. A final decision could take months and will be made in consultation with the victims’ families.

Aurora, Colo. police chief Dan Oates claims the suspect “lawyered up” and he believes it could be months before police learn what motivated the massacre at the Century 16 cinemas in the Denver suburb at a midnight screening of the Batman film The Dark Knight Rises.

Twelve people were killed in the shooting and 58 were wounded. A vigil was held Sunday for the victims. U.S. President Barack Obama visited those recovering in hospital.

The rifle used during the attack reportedly jammed, forcing the gunman to switch to a weapon with less firepower and inadvertently saving lives.

Police allege Holmes burst into the theatre just after midnight on Friday, tossed a couple of gas canisters and began firing on the audience. He was allegedly clad in full body armour, a ballistic helmet and gas mask. A semi-automatic assault rifle, a shotgun and a pistol were used in the attack, police said.

The suspect was a doctoral student in neuroscience at the University of Colorado’s Anschutz Medical Campus and school officials are trying to determine if he collected hazardous materials during his time in the program. He dropped out last month — a year into the up to seven-year program — for unknown reasons.

The university hasn’t released any details of Holmes’ academic record. The school disabled its website for the neuroscience graduate program over the weekend and professors have been advised not to speak with reporters.

Holmes has been described as a strong student and an introvert, by former friends and neighbours.
Police allege Holmes began buying guns at stores in the Denver area two months before the attack and had received up to 50 packages in the past four months, delivered to his home and at school. He allegedly ordered 6,000 rounds of ammunition online.

When officers arrived at his north Aurora apartment on Friday morning they found it had been rigged with sophisticated booby-traps, including volatile explosive chemicals, police said.

The suspect applied last month to join a gun club in Byers, Colo. but was denied, due to his behaviour and a “bizarre” message on his voicemail, according to the owner of the Lead Valley Range, Glenn Rotkovich.

With files from The Associated Press