Who Is James Holmes? Suspected Shooter Is 24, Was University Of Colorado Student

The suspected shooter's only past brush with police was a traffic ticket in 2011.

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Law enforcement has identified James Holmes, 24, as the suspected shooter who opened fire at a midnight premiere of The Dark Knight Rises in Aurora, Colo. Friday, killing 12 people and injuring 59. "Many" people are in critical condition, according to authorities.

Holmes, who wore all black, a ballistic vest and a gas mask during the shooting, was arrested by authorities shortly after. He used three weapons--an assault rifle, shotgun and handgun--in the shooting, all of which were legally purchased at local gun stores within the last few months, according to NBC.

Aurora Police Chief Dan Oates said “many, many rounds were fired.”

He also said police were "not looking for any other suspects" and were "confident [Holmes] acted alone."

Holmes had been a student at the University of Colorado, but withdrew last month, according to the university. He was getting a PhD in neuroscience. A "James Holmes" is listed as enrolled in a class at the university called  "Biological Basis of Psychiatric and Neurological Disorders."

Holmes also received a B.S. in neuroscience from the University of California Riverside in 2010, where he graduated with honors.

On an apartment rental application, Holmes described himself as "quiet" and "easy-going."

[Read: Tweets From Victims, Survivors During The Shooting]

According to MSNBC, Holmes is from the San Diego area, and once lived in Riverside. He graduated from Westview High School in San Diego in 2006.

San Diego resident Arlene Holmes told ABC News she was the suspect's mother, and that she believed her son was the culprit. "You have the right person," she said.

Holmes' only past brush with police was a speeding ticket in 2011. 

A man who claims to live across the street from Holmes has shared photos on Reddit of law enforcement officials patrolling an apartment building believed to belong to Holmes. Police say Holmes' apartment building is located at 1690 Paris St. in Aurora, not far from the Century 16 theater where the shooting took place.

Authorities are currently entering the apartment with caution, as the apartment is booby-trapped with explosives, chemical devices and buckets of ammunition, according to police. Residents in five buildings in the area have been evacuated. Police say it could take days to clear Holmes' apartment.

U.S. News reporter Seth Cline contributed to this report.

Elizabeth Flock is a staff writer for U.S. News & World Report. You can contact her at eflock@usnews.com or follow her on Twitter and Facebook.