27-year-old James Holmes who walked into a Aurora, Colorado movie theater, and fatally shot 12 people and injured 70 others on 20 July 2012 was found guilty of first-degree murder on Thursday afternoon for the theater massacre three years ago.

According to the Colorado Springs Gazette reports, Holmes was initially charged with 24 counts of murder and 140 counts of attempted murder — two for each person killed and two for each injured. He was also charged with possession of explosives.

Holmes plea of not guilty by way of insanity was refuted by District Attorney George Brauchler.

“He only stopped when the gun stopped… We know what insanity is… this ain’t it. He knew what he was doing when he killed those people. He intended to kill them. That was his specific goal.”

Prosecutors sought the death penalty and Holmes pleaded not guilty by reason of insanity on 4 June 2013.

The tragedy is said to be one of the worst shootings in US history.