Los Angeles - A psychiatrist treating alleged US cinema shooter James Holmes declined a police offer to detain him for mental health checks after he talked about killing "a lot of people", reports said on Thursday.
Psychiatrist Lynne Fenton called University of Colorado police to voice concern about Holmes, weeks ahead of the July massacre which killed 12 people and wounded 58 more at a screening of Batman movie The Dark Knight Rises.
The campus medic had been treating Holmes, but became alarmed when he talked to her on 11 June of fantasising about killing "a lot of people", according to a source cited by the Denver Post newspaper.
She asked for a police background check, which showed he had no criminal record, the Post and local ABC7 television reported.
A campus police officer asked Fenton if the 24-year-old should be detained for a 72-hour psychiatric "hold" to assess his mental health, a decision the medic was qualified to take, the unidentified sources said.
But Fenton, who had herself set up a campus-wide threat-assessment team years before, declined the offer, and the threat was not followed up on, in part because Holmes was in the process of leaving the university, ABC7 reported.
On 20 July, Holmes allegedly opened fire on a packed cinema at a midnight premiere screening of the new Batman movie, in one of the deadliest shootings in recent US history.
The student, who reportedly wore body armour and a gas mask and threw smoke bombs into the cinema before starting to shoot, looked befuddled and wide-eyed when he first appeared in court after the alleged killings.
Sporting bright orange hair which drew comparisons with Batman's arch rival the Joker, he has been in solitary confinement since being detained in Aurora, just outside Denver.
Holmes could face the death penalty if convicted, although Colorado has only executed one person since capital punishment was reinstated in the western US state in 1976.