James Holmes was found guilty of first-degree murder in the 2012 Aurora, Colo., movie theater shooting that killed 12 people and injured 70 others, CNN reports.

Holmes, who had pleaded not guilty by reason of insanity, was convicted on all 164 counts of murder and attempted murder, two counts for each of the victims, along with one count of possession or control of an explosive or incendiary device.

After the 10-week trial, it took the jury approximately 12 hours in deliberations to convict Holmes. The same jury will begin the sentencing phase next Wednesday, where the prosecution will be seeking the death penalty.

"We are very happy that this animal, that this monster, will never see the light of day," said Sandy Phillips, the mother of victim Jessica Ghawi.

On July 20, 2012, Holmes walked into a midnight screening of The Dark Knight Rises wearing a ballistic helmet, gas mask, black gloves and protective gear. He released tear gas into the theater before opening fire with an AR-15 rifle, a 12-gauge shotgun and a .40 caliber handgun.