JAMES Eagen Holmes came from a well-tended San Diego enclave of two-storey homes, where neighbours recall him as a clean-cut, studious young man of few words.
The son of a nurse, Arlene, and a software company manager, Robert, Holmes was a brilliant science scholar in college.
The biggest mystery surrounding the 24-year-old doctoral student was why he would have pulled on a gas mask and shot dozens of people early on Friday in a suburban Denver cinema, as police allege.
In the age of widespread social media, no trace of Holmes could be found on Facebook, LinkedIn, MySpace, Twitter or anywhere on the web.
A longtime neighbour in San Diego, where Holmes grew up, remembers only a "shy guy ... a loner" from a churchgoing family. In addition to playing soccer at school, he ran cross country.
The bookish demeanour concealed an unravelling life. Holmes struggled to find work after graduating with highest honours in spring 2010 with a neuroscience degree from the University of California, Riverside, said the neighbour, retired electrical engineer Tom Mai.
Holmes enrolled last year in a neuroscience PhD program at the University of Colorado-Denver but was in the process of withdrawing, said school officials.
In academic achievement, "he was at the top of the top," recalled Riverside Chancellor Timothy P. White.
Holmes concentrated his study on "how we all behave," White added. "It's ironic and sad."
There are no indications he had problems with police.
His life appears to be unblemished, a clever young man with unlimited potential.