"It was this deep, guttural voice, rambling something incoherent," Rotkovich said. "I thought, 'What is this idiot trying to be?'"
Rotkovich said he told his employees Holmes was not allowed on the premises
Had Holmes been allowed on the range, he could have practiced with the guns found in his possession when he was arrested in the back of the Century 16 movie theater in Aurora on Friday morning. Police say he had an assault-style rifle, a shotgun and two .40- caliber handguns.
Holmes allegedly set off canisters of noxious gas and then opened fire on a crowd watching the midnight premiere of "The Dark Knight Rises," killing 12 and wounding 58 others before surrendering to police and telling them there were explosives in his apartment.
A federal law enforcement official told The Associated Press that the gunman's semiautomatic rifle jammed during the attack, forcing him to switch to another gun. That malfunction and weapons switch may have saved some lives.
Since the shooting, police, FBI and ATF agents have been methodically retracing Holmes' steps as they assemble evidence in one of the worst mass murders in U.S. history.
On Sunday, the door to Holmes' apartment at 1690 Paris St. in Aurora remained screwed shut as local police awaited special investigators from the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives.
Residents of the three-story building, where Holmes' apartment was rigged with explosives that Aurora Police Chief Dan Oates said were meant to kill anyone who walked through the door, were not allowed to return home. But police did retrieve whatever belonging people evacuated since Friday needed from inside their homes.
Dmitry Shchekochikhin, 27, a student at the Anschutz Medical Campus from Moscow, returned home Sunday at 8 a.m. to retrieve belongings including his laptop, cellphone, passport and medical text books.
Shchekochikhin has had a first-floor apartment in the building since November and said he often encountered Holmes.
"Whenever I said hello or greeted him, he would never say anything back," said Shchekochikhin. He said that Holmes wore casual clothing, "nothing special."
A man who lives across the hall from Holmes was not comfortable giving his name for publication, but said Holmes recently dyed his hair red.
As police retrieved his belongings, that same neighbor said Holmes had male and female visitors from time to time, but never anyone who drew attention. He also said Holmes was a quiet neighbor, never playing his TV or stereo too loudly.
That was true until Thursday night, when Holmes left the stereo turned up loud, with a song playing on repeat. Downstairs neighbor Kaitlyn Fonzi went up to ask him to turn the music down and found the door slightly ajar. She said Friday that she had reached for the doorknob, but decided not to go in.
On Saturday, police and bomb squad personnel removed 30 softball-sized improvised explosive devices in the living room of Holmes' 800-square-foot apartment.
Although Holmes' unit had been cleared of explosives, there still may be hazardous materials inside. Police said it may be Tuesday before residents can go home.
Those dangerous materials, along with magazines for firearms and ammunition, are believed to have been purchased through the mail, not taken from the University of Colorado Anschutz Medical Campus where Holmes was a graduate student.
Police evacuated two research buildings that Holmes had key-card access to while he was a student in a neurosciences program on the Anschutz Medical Campus on Friday. The buildings were searched by bomb-detection dogs, Oates said.
"We did a thorough search of those facilities, and, as we'd hoped, there were no hazards found," he said.
Oates would not specify what materials Holmes had delivered to his home but said they indicated a level of premeditation.
"There is some evidence here, I think, of some calculation and deliberation," Oates said.