Police in Aurora, Denver are trying to put together details of the life of 24-year-old James Holmes, the man suspected of Friday's shooting spree. He seems to have have kept a very low online profile: there is so far no trace of him on Facebook, MySpace or Twitter.
Born 13 December 1987 in San Diego County, California
Graduated from Westview High School in 2006
Won a scholarship to University of California Riverside
Graduated with a bachelor's degree in neuroscience in 2010
Enrolled in doctoral programme at University of Colorado at Denver in June 2011
Before coming to Denver, Holmes lived in San Diego, where he went to high school. Neighbours remember him as "clean-cut, quiet and studious."
His mother Arlene is a nurse, whilst his father Robert works as a software company manager.
Chancellor of the University of California Riverside, Timothy White, described Holmes as a gifted student:
White said he concentrated his study "on how we all behave...It's ironic and sad."
After graduation Mr Holmes returned to San Diego, where he is said to have struggled to find a job. Eventually, he got part-time work at McDonald's.
He then went on to study for a graduate programme in neuroscience at the University of Colorado, Denver. A spokeswoman says he was in the process of withdrawing.
Fellow research assistant Billy Kromka described him as "socially awkward:"
In the days leading up to the cinema attack, Holmes legally bought four weapons at local gun shops:
An AR-15 semi-automatic assault rifle
Two .40 calibre Glock handguns
A 12-guage Remington shotgun.
Aurora police chief Dan Oates confirmed the weapons were obtained legally:
New York Police Commissioner Ray Kelly, who is thought to be in contact with the Aurora police chief described him as "a clearly deranged individual."
Holmes has no criminal record from either San Diego or Riverside. He lived in an apartment across the street from the campus.
Katie Fonzi, a 20-year-old biology student at the University of Colorado Denver lives in the apartment below.
She told reporters she heard techno music blasting from inside his apartment at around midnight when Holmes is believed to have been at the theatre. At 1am, she said the music stopped.
Bomb technicians from Colorado are getting help from the government to untangle the potentially explosive mess left in his apartment, which remains evacuated.
Aurora Deputy Fire Chief Chris Henderson said they found a number of liter-sized lemonade bottles filled with an unknown liquid connected with wires inside, according to the Denver Post.
Denver FBI said emergency workers are working on "how to disarm the flammable or explosive material" inside.
Holmes is in custody, and is not thought to be co-operating with police.
His family released a statement saying:
He is expected to make his first court appearance on Monday.