A police officer said Aurora, Colo., theater suspect James Holmes didn’t show any “outward emotion or any outward sign of engagement” when he and another officer arrested him following the July 20, 2012, shooting rampage during a late-night screening of “The Dark Night Rises.”

Jason Oviatt, an officer with the Aurora Police Department, said he at first thought the suspect could have been another officer as he was wearing a gas mask and what looked to be like SWAT gear, standing beside a white car in the back of the theater. The suspect, whom Oviatt identified as Holmes, did not attempt to flee as he was apprehended and responded to their directions.

Holmes is charged with killing 12 people and injuring 70 others in the shooting rampage. He has pleaded not guilty by reason of insanity.

Oviatt described the suspect as calm during his arrest, occasionally looking around at a passing car or someone shouting, in what was a chaotic situation outside the Century Theaters multiplex.

He asked the suspect, whose hair was dyed orange, whether there were other assailants, but Holmes told him, “It’s just me.”

The officers removed the suspect’s helmet and gas mask, but found that he was wearing body armor. Oviatt needed the help of other officers to search him thoroughly, and removed two knives and a handgun magazine from his pocket.

Officer Jason Sweeney, who was with Oviatt in making the arrest, testified that he also thought Holmes was another officer before realizing that he was a suspect.

Officers noticed the light of a laser beaming from the suspect’s car. As it turned out, it was from a handgun that was on top of the car.

Another officer testified about being with the suspect in the back of the police car when the suspect talked of having explosive devices at his apartment.

Later in the day, prosecutors played security camera footage of the suspect milling about the concession stand area before entering the theater.