James Eagan Holmes was born on December 13, 1987, in San Diego, California, to a family that appeared, on the surface, to be stable and supportive. His father, Robert Holmes, was a mathematician and scientist, while his mother, Arlene, was a registered nurse. Holmes grew up in a relatively quiet, middle-class neighborhood. As a child, he was described as bright, shy, and introverted. Teachers and classmates noted his academic strengths, particularly in science, though he often struggled with social interactions.

He attended Westview High School in San Diego and later enrolled at the University of California, Riverside, where he graduated with honors in neuroscience. After that, Holmes was accepted into the University of Colorado's neuroscience Ph.D. program in Aurora. While in graduate school, his mental health began to noticeably deteriorate. He became increasingly withdrawn and failed important oral exams, which led to him dropping out of the program in June 2012—just one month before the mass shooting.

At the time, Holmes was already showing signs of severe mental illness. He had reportedly been seeing a psychiatrist and had expressed disturbing thoughts during sessions, including fantasies about killing others.

On the night of July 20, 2012, James Holmes entered a Century 16 movie theater in Aurora, Colorado, during a midnight screening of The Dark Knight Rises. Dressed in tactical gear and armed with multiple weapons—including an AR-15 rifle, a shotgun, and a handgun—he opened fire on the crowded audience. The rampage left 12 people dead and 70 others injured, with 62 directly shot and 8 suffering injuries while fleeing. It was one of the deadliest mass shootings in modern U.S. history.

Holmes had planned the attack meticulously. He stockpiled weapons and ammunition over the course of months and even booby-trapped his apartment with explosives, which police safely defused the day after the massacre. Authorities found Holmes waiting outside the theater next to his car and arrested him without incident. He told police he was “The Joker,” though this was later debated and not consistently corroborated.

Holmes was held without bail and underwent several psychiatric evaluations. He attempted suicide multiple times while in jail. He entered a plea of not guilty by reason of insanity, and the court accepted it. His trial began on April 27, 2015, and lasted several months. Despite testimony about his mental health and evidence of schizophrenia, the jury found Holmes guilty on 165 counts, including first-degree murder and attempted murder.

On July 16, 2015, Holmes was convicted, and on August 15, 2015, he was sentenced to 12 consecutive life terms without parole, along with 3,318 additional years. The jury chose life in prison over the death penalty by a single vote. The judge made it clear that Holmes would never be allowed to reenter society. He is currently incarcerated at an undisclosed location for safety reasons, reportedly in a federal prison outside Colorado.