James Holmes has been found guilty of shooting dead 12 people during the premier screening of Batman in Aurora, Colorado.
The horrific incident- which took place in 2012- hit headlines around the world and led to an outpouring of grief in the stricken town.
Holmes, 27, was found guilty of 12 counts of murder as well as multiple counts of attempted murder.
His lawyers claimed her was suffering from mental health problems and the former PhD student plead guilty on the grounds of insanity.
Jurors rejected his claims, leading the guilty verdict.
Prosecutor George Brauchler said during the court session: "They came in hoping to see a story of a hero dressed in black, someone who would fight insurmountable odds in the name of justice and trying to protect others.
"Instead a different figure appeared by the screen dressed all in black.
"And he came there with one thing in his heart and in his mind - and that was mass murder."
According to the BBC, prosecutors will now seek that he is sentenced to the death penalty.
Holmes had no previous criminal record when he entered the Aurora cinema with a pistol, assault rifle and shotgun.
The youngest person killed during the horrendous massacre was a 6-year-old girl. Her mother suffered a miscarriage following her injuries and has been left paralysed.
Holmes will be sentenced later on this summer.