Updated at 6:30 p.m. ET
CENTENNIAL, Colo. With some families of shooting victims of the Colorado movie theater massacre listening, police officers fought to keep their composure Monday as they testified about their efforts to try to save the wounded without enough ambulances.
During the opening of a hearing in which prosecutors began laying out their case against James Holmes, the officers testified the movie was still playing as they entered the theater. An alarm was going off and moviegoers' cellphones rang unanswered. There was so much blood on the floor, Officer Justin Grizzle said he slipped and almost fell down.
Investigators say Holmes tossed two gas canisters and then opened fire during the midnight showing of the Batman movie "The Dark Knight Rises" on July 20, killing 12 people and wounding dozens.
"He's heartless. He really is. He has no emotion. He has no feeling. I don't know anybody can live that way," Sam Soudani told The Associated Press after the hearing. His 23-year-old daughter survived after being hit by shrapnel from an explosive device at the theater.
CBS correspondent Barry Petersen reports that Specialist Sergeant Gerald Jonsgaard was close to tears as he described how he came across 6-year-old victim Veronica Moser Sullivan. "I checked for a pulse," he said. "She was dead no pulse."
Veronica's great aunt, Mary Ellen Hansen, was one of several family members of the dead inside the courtroom Monday.
"It was gut-wrenching, it really was, to think that a 6-year-old's life was snuffed out in seconds. And it made me feel like I was reliving that."
Officer Grizzle recalled ferrying the wounded to the hospital and said he had to stop one man worried about his 7-year-old daughter from jumping out of the moving patrol car. He said there was so much blood in his car that he could hear it sloshing around.
A bearded Holmes didn't appear to show any emotion.
Police officers who arrested the suspected gunman described the former neuroscience graduate student, clad in body armor, as unusually relaxed but fidgety at times.
Holmes didn't resist arrest behind the theater and volunteered that his apartment had been booby trapped, the officers testified.
When Officer Jason Oviatt first saw Holmes in his gear standing next to his car behind the theater, he thought he was a fellow officer but then realized Holmes was standing still, and not rushing toward the theater.
Oviatt said Holmes seemed "very, very relaxed" and didn't seem to have "normal emotional reactions" to things.
"He seemed very detached from it all," he said.
Oviatt pointed his gun at him, handcuffed him and searched him. He said he found two knives and a semi-automatic handgun on top of Holmes' car. Oviatt said an ammunition magazine also fell out of Holmes' pocket and he found another one on the ground. He said Holmes was dripping in sweat and his pupils were wide open.
Officer Aaron Blue said Holmes was fidgeting around after he and Oviatt put him in a patrol car, prompting them to stop and search Holmes again. They were worried they might have missed something because of Holmes' bulky outfit.
Police found that Holmes bought the ticket on July 8, almost two weeks before the July 20 shooting, Petersen reports. Surveillance video showed Holmes acting so normal in the lobby that night, he opened a door for a couple and politely let them go in.
The preliminary hearing is expected to last all week. It will allow the judge to determine whether the prosecution's case is strong enough to warrant a trial but it's rare for a judge not to order a trial if a case gets this far.
CBS News senior legal analyst Andrew Cohen reports the prosecution has a low burden to meet at the hearing, but notes that the proceeding allows the defense an early chance to evaluate the strength of the state's case and to question law enforcement officials.
"It's likely to be dramatic and in many ways heartbreaking," Cohen told CBS Radio News. "The public will hear details for the first time about what police believe went on inside that theater. We could hear 911 tapes. There will likely be photos and video, and Holmes will be at the defense table through it all."
Whatever other details emerge at the preliminary hearing, they will do so in a nation that has changed dramatically since the July 20 attack that pushed the problems of gun violence and mental illness into the forefront before receding.
That debate reignited last month when a gunman killed 20 children and six adults at Sandy Hook Elementary School in Newtown, Conn., spawning calls for better psychiatric care, tougher gun laws and the arming of teachers.
Holmes is charged with more than 160 counts, including murder and attempted murder.
Legal analysts say that evidence appears to be so strong that Holmes may well accept a plea agreement before trial.
In such cases, the preliminary hearing can set the stage for a deal by letting each side assess the other's strengths and weaknesses, said Laurie Levenson, a former federal prosecutor and now a professor at Loyola Law School in Los Angeles.
They "are often the first step to resolving the case, a mini-trial so both sides can see the writing on the wall," she said.