Who is James Holmes? A portrait of the Colorado “Joker” killer.

New reports give details about James Holmes, the psychotic gunman who killed 12 people at a screening of the new Batman film on Thursday night.

James Holmes, 24, was a PhD student who was described as “really smart” but was in the process of dropping out of graduate school at the University of Colorado Denver.

He is said to have had few friends and barely any social life, instead spending hours indoors playing the video game Guitar Hero.

Police are currently baffled as to Holmes’s motives for launching the deadly attack which injured 71 people as they watched blockbuster The Dark Knight Rises at a midnight showing in Aurora, a suburb of Denver.

However, one clue may come in a report that the killer, whose family comes from San Diego, had dyed his hair red and described himself as “the Joker”, implying that he was inspired by the popular Batman series itself.

Although James Holmes described himself as “easy-going”, neighbors and classmates recalled an anti-social recluse who had little contact with others.

Officials do not currently believe that the gunman had terror links, adding to the mystery of his possible motives.

“It clearly looks like a deranged individual,” NYPD police chief Ray Kelly said.

“He had his hair painted red. He said he was <<The Joker>>, obviously the enemy of Batman.”

A neighbor also reported that police, who were searching James Holmes’s apartment for explosives, asked him if he had seen “a white guy with crazy hair, possibly dyed unnatural colors”, the Denver Post said.

But neighbors at university housing in Denver described James Holmes as a recluse who kept himself to himself. One student said: “No one knew him. No one.”

James Holmes – who had been working towards his PhD for a year before dropping out – had one techno song blaring from his stereo in the hours before the massacre and left the music on repeat in his booby-trapped apartment as he departed to commit the massacre.

He was also reportedly addicted to video game Guitar Hero.

His shocked mother in San Diego confirmed that he was behind the massacre, telling reporters: “You’ve got the right man.”

After graduating from Westview High School in 2006, James Holmes studied neuroscience at the University of California Riverside, where he graduated with honors.

Neighbors in California said that James Holmes moved to Colorado to attend graduate school after failing to find a job.

The university said he was dropping out because of academic issues, and had not had any disciplinary problems.

The gunman described himself as “quiet and easy-going” in a rental application last year, and high school classmates confirmed that impression in interviews with the Los Angeles Times.

Dan Kim, currently a student at UC San Diego, said: “He didn’t seem like a troublemaker at all. He just seemed like he wanted to get in and out, and go to college.”

James Holmes ran in Westview’s cross country team with Tori Burton, who said: “He was very quiet. He was a nice guy when you did occasionally talk to him. But he was definitely more introverted.”

Another classmate, Keith Goodwin, spoke of his shock at seeing the “generally pleasant” young man hit the news for his role in the massacre.

“James was certainly not someone I would have ever imagined shooting somebody,” said Keith Goodwin.

James Holmes has only ever had contact with police over a traffic violation, according to the New York Times, who spoke to two law-enforcement officials about the gunman.

“He’s not on anybody’s radar screen,” said one official, while the other added: “This guy is somewhat of an enigma. Nobody knows anything about him.”

The killer’s family appealed for privacy as they described their anguish at seeing James Holmes involved in massacre.

“Our hearts go out to those who were involved in this tragedy and to the families and friends of those involved,” they said in a statement released by San Diego police.

“We ask that the media respect our privacy during this difficult time.

“Our family is cooperating with authorities in both San Diego, California and Aurora, Colorado. We are still trying to process this information and we appreciate that people will respect our privacy.”

Jackie Mitchell, a furniture mover who lives several blocks from the suspect’s apartment building in Colorado, said he had drinks with James Holmes at a local bar on Tuesday night, though he gave no sign of being distressed or violent.

After James Holmes approached him “we just talked about football. He had a backpack and geeky glasses and seemed like a real intelligent guy, and I figured he was one of the college students,” Jackie Mitchell said.

When Jackie Mitchell saw James Holmes’s photo after the shooting, “the hair stood up on my back,” he said.

“I know this guy.”

Another neighbor, Rachel Reed, said she met James Holmes in a local bar when she put rap music by Lil Wayne on the jukebox.

He came over and “made some racially charged comments about rap,” she said. “He seemed like he was a normal dude. He was a little buzzed.”

James Holmes is not talking to police and has asked for a lawyer, according to a law enforcement official briefed on the investigation.

His first court appearance is set for Monday morning at 9.30.