James Holmes was on Tuesday described by a psychiatrist who treated him as an anxious, antisocial oddball who thought obsessively about killing people for months before he opened fire in a crowded movie theatre in Denver killing 12 and wounding 70.

According to CNN, Dr Lynne Fenton testified before a packed courtroom that Mr Holmes had testified this to her in March 2012. Dr Lynne stated that Holmes had confided that he had “Homicidal thoughts” as often as four times in a day. She added that as his treatment progressed, he told her his killing obsession was getting worse.

Dr Fenton told the jury that there was very little she could do because Holmes had never talked about specifics. She was unable to place him on psychiatric hold since he had not disclosed intentions to kill anyone in particular.

Dr Fenton, Who headed the student mental health clinic at the University of Colorado, was perhaps the most anticipated witness at Holmes Capital murder trial.

Fenton disclosed that she had treated Holmes from mid-march until June 11, when he left her care upon dropping from his postgraduate course in neuroscience. He had walked out of her office without shaking her hand or even saying goodbye.

After one month, on July 20, 2012, Holmes tossed a tear gas canister into Theatre 9 at the Century 16 multiplex and shot into the audience during the premiere of “The Dark Knight Rises.”

Before the attack, Holmes emailed Fenton a notebook containing elaborate sketches of the theatre, details of his plans and his reasons for carrying out the attack.

Holmes has pleaded not guilty by reason of insanity, in case he is convicted of murder, prosecutors intend of seeking the death penalty.

Fenton and the university are being sued by the relatives of some of the victims, and she had never spoken publicly about her seven meetings with Holmes.