Suspect in mass shooting left his graduate programme at the University of Colorado last month, but no motive is yet known

This article is more than 8 years old

This article is more than 8 years old

The gunman suspected of one of the worst shooting rampages in recent US history is a neuroscience graduate who dropped out of his PhD course last month.

As Colorado reeled from its latest mass killing, details were starting to emerge about James Holmes, 24, who was in police custody after shooting at least 12 people dead and injuring close to 60 others at a screening of latest Batman movie, The Dark Knight Rises.

The only photograph yet to emerge of the suspect depicts a smiling 20-something with short hair – a quite different image from the heavily-armed shooter dressed all in black that survivors of the attack have described.

Holmes, who had no criminal record and was unknown to the authorities, was originally from San Diego and had moved to Colorado in 2011 for a graduate course in neuroscience at the University of Colorado School of Medicine. But last month he withdrew from the course, the university said.

A spokesman for the centre told the Guardian: "He enrolled in the university in June 2011 and was in the process of withdrawing from the school."

Due to privacy rules covering students, the spokesman could not comment on whether he had been in any trouble at the university, or if his withdrawal from classes was voluntary or not.

He had been studying at the University of Colorado Denver Graduate Programme in neuroscience, the institution confirmed.

Documents show that a James Holmes had been enrolled on a course called Biological Basis of Psychiatric and Neurological Disorders. He gave a presentation on May 8 on the topic of "MicroRNA biomarkers."

He had previously graduated from the University of California in spring 2010 with a BSc in neuroscience.

Holmes was described as the "top of the top" in academic terms by his former university.

Timothy White, chancellor of University of California, Riverside, said: "He was an honours student, so academically he was top of the top. He distinguished himself from an academic point of view in his four years with us."

The suspect's mother reportedly told a neighbour at the family home in California that that Holmes couldn't find a job after finishing his studies.

Speaking to the Associated Press, Tom Mai said the family had lived in a well-to-do part of San Diego for about 10 years.

Holmes's mother is a nurse and his father worked at a software company, Mr Mai said. The neighbour described the couple's son - whom he spoke to on occasion only to say 'hello' – as shy and a loner.

The FBI said Friday that they knew of no ties between the suspect and any terrorist or militia group. The only previous brush with the law was a traffic summons for speeding in October 2011.

In Aurora, attention focused on the apartment in Paris Street, where Holmes lived. On Friday, forensic and explosives experts searched his home for booby-traps. A camera mounted to a pole was used to look inside the apartment, with police using a laddered fire truck to reach the property.

Holmes lived alone in the small one-bedroom property, which is situated just a few miles away from the movie theatre in which the gun rampage took place.

Meanwhile in San Diego, where Holmes attended high school, reporters besieged the house of his parents.

Speaking outside the property, Andra Brown of the San Diego police department, said the family contacted the local police after becoming concerned when members of the media turned up.

ABC News had earlier reported that a woman at the house, identifying herself as the gunman's mother, spoke to reporters to confirm that they "had the right person".

At a press conference, Lt Brown said: "The Holmes family is very upset by all of this. It is a tragic event and has taken everybody by surprise".