CENTENNIAL, Colo. -- A police officer testified at a preliminary hearing here on Monday that when he responded to emergency calls about a mass shooting at a crowded movie theater this summer, he found the suspected gunman standing calmly outside his car in a parking lot just moments after the man had opened fire inside, the authorities say, killing 12 people and injuring 58 others.
"He was very relaxed," said the police officer, Jason Oviatt. "It was like there weren't normal emotional responses to anything. He seemed very detached."
Officer Oviatt said that because the suspect, James E. Holmes, had been wearing a helmet and a gas mask, he had first thought that he was a fellow police officer.
"He was just standing there," said the officer, as all around them panic-stricken people fled the theater as quickly as they could, many with bullet wounds, many others covered in blood.
But after a few moments, Officer Oviatt realized that aside from his calm demeanor, there was something else dangerously amiss about the man, whom he had first seen standing perfectly still -- his hands were oddly positioned on the roof of his white car.
He noticed that Mr. Holmes, who was wearing a red jumpsuit, was sweating profusely and that he was emitting a very foul body odor.
Then, as he placed the compliant Mr. Holmes into handcuffs, the officer learned why Mr. Holmes may have been standing in such an unusual way, reluctant to move: a handgun was lying on the roof of the car where Mr. Holmes's hands had been.
While frisking Mr. Holmes, he said, he found that he was swathed in layers of body armor, which officers eventually had to cut off with knives to search him adequately.
Police officers were among the first people to testify at a weeklong court hearing that will determine whether there is sufficient evidence to move the case against Mr. Holmes to trial, a decision that will be made by William Sylvester, a district judge in Arapahoe County.
But for victims and their families, the hearing may offer the best, and perhaps only, opportunity to understand how the July 20 shooting unfolded, and to get a glimpse into Mr. Holmes's actions and mind-set in the weeks before the attack. A criminal trial -- if one ever convenes -- remains months away, probably at the end of a long series of legal arguments, including over Mr. Holmes's mental fitness to stand trial.
It has been more than five months since Mr. Holmes, a neuroscience graduate student, was accused of striding into a midnight screening of "The Dark Knight Rises" at a movie theater in an Aurora shopping mall and began shooting.
He faces more than 160 counts of first-degree murder and attempted murder.
On Monday, police officers described the scene inside the theater in graphic terms, describing amounts of blood on the floor so copious that they had trouble keeping their footing. As the movie played on and cellphones rang incessantly, the officers said, they went from person to person, checking for signs of life.
"They were screaming, they were yelling: 'Help us! Help us!'" said Justin Grizzle, a police officer who was among the first to respond.
Realizing that there were not enough ambulances to transport all the injured to hospitals, the officer said, he began putting people in his patrol car. He made four trips to the hospital, he said. By the end, he could hear the sloshing sound of blood in the back of the car, he said.
Lawyers for Mr. Holmes, 25, have signaled that they might call witnesses this week to discuss his mental state in the hope of rebutting the prosecution's evidence that Mr. Holmes spent months methodically buying 6,000 rounds of ammunition, handguns, a shotgun and an assault rifle. He had also booby-trapped his apartment with explosives, which he told the police about after he was arrested.
The fact that Mr. Holmes did not kill himself, unlike gunmen at Sandy Hook Elementary School, Columbine High School or Virginia Tech, has transformed the aftermath of the tragedy into a trying and costly legal case.
Although Mr. Holmes has not yet filed a plea, his lawyers have said several times that he is mentally ill. Mr. Holmes had seen a psychologist at the University of Colorado, Denver, where he had been a graduate student, and had so alarmed his doctor that she contacted the campus police about him.
Less than a month before the shooting, after he had dropped out of his neuroscience program, Mr. Holmes sent a text message to a classmate that suggested he believed that he suffered from dysphoric mania, a bipolar condition that combines manic behavior and dark, depressive tendencies. Mr. Holmes warned the classmate to stay away from him "because I am bad news," the classmate has said.
This article originally appeared in The New York Times.