If One L Goh, the 43-year-old Korean who allegedly shot and killed seven people at a private Christian college, Oikos University, in Oakland California on Monday, was seeking notoriety, it did not last long. By lunchtime yesterday the story had already disappeared from the front page of the BBC news website. School shootings are so common in the US that we have become almost inured to them.

What made him do it? And why should the US in particular be prone to such attacks? They are far more frequent in America than elsewhere in the world (though appalling atrocities have occurred in Russia, Israel and a number of European countries).

According to Oakland Police Chief Howard Jordan, Goh was "upset with the administration at the school" where he had been a student, until he was expelled a few months ago.

He complained that students had "mistreated him, disrespected him, and things of that nature", Mr Jordan said. "He was having, we believe, some behavioural problems at the school and was asked to leave several months ago."

In addition to his troubles at school, Goh owed thousands of dollars in tax and recently suffered two bereavements, including the death of his mother.

Most perpetrators of school massacres had struggled to cope with personal failure or significant losses prior to the attack, research shows. Many had attempted suicide or behaved in other ways that looked like a cry for help.

Yet personal failure and loss are universal experiences. There are many other potential factors – bullying and revenge, mental illness, exposure to violent films and video games, drugs, access to guns. Which of these account for the higher incidence of attacks in the richest country in the world?

After the infamous Columbine shootings in 1999, when Eric Harris and Dylan Klebold killed 12 students and a teacher, the US Secret Service and the US Department of Education established an inquiry that examined 37 similar shootings between 1974 and 2000.

It concluded there were common threads. Shootings were rarely sudden, impulsive acts – in most cases other people knew about the attacker's plans.

Although there was no accurate "profile" of an attacker – attempts to predict which individuals will commit such acts are doomed to fail – most behaved in ways that indicated they needed help. Many felt bullied or persecuted and there were often signs that they were planning for an attack.

The result was the Safe School Initiative, which aimed to help university staff and police share information about possible threats and develop strategies to prevent potential attacks.

In a recent article, "Why does America lead the world in school shootings?", Frank Ochberg, Professor of psychiatry at Michigan State University observed: "Students do not become mass killers overnight. They nurse their fantasies and they leak evidence. Insults, threats and plans are posted on websites. Classmates often know when a student is ready to strike back. Parents hear rumblings and have accurate gut sensations."

New programmes to share information led to several plots being nipped in the bud, he said. Other countries adopted similar programmes. Yet America is still the one where these tragedies happen most.

There is no evidence, Professor Ochberg says, that, compared to other nations, America has "more bullies, more bullying, more victimisation, and more victims who are ticking time bombs, hatching plots of lethal vengeance".

Mental illness has been a feature in some killings. People with mental illness are very rarely violent – they are far more likely to be the victims of violence. But occasionally they can become a danger to others.

"We do not have a sophisticated system of care and protection," Professor Ochberg says. Community care for the mentally ill was "never fully funded" and "leaves much to be desired". But, he adds, America in this regard is "really no worse than other nations".

Violence is ever present – on TV screens, in video games and movies – and many commentators have suggested this can lead to copycat behaviour and desensitisation to its effects. Others counter that it acts as catharsis, defusing potential violent acts.

Professor Ochberg notes that violent role models have a long history and are not limited to America. "Northern Ireland, the Balkans, the children's armies of Africa, the terrorist camps of the Middle East, have their violent role models. Machismo is not an American word, nor is hooligan."

What is left? One factor that, for many, defines America is access to guns. If kids could not bring guns to school, we wouldn't have Columbine or Virginia Tech (where 32 people were slaughtered by 23-year-old student Cho Seung-hui in 2007). Or, now, Oakland, Professor Ochberg might have added.

"The reason we have an American school shooting problem that exceeds other nations has to do with access to loaded weapons by kids who should not have that access. Any serious attempt to prevent school shooting will have to attack the problem," he said.

It is not a view likely to win wide support, especially in states with a powerful gun heritage. Some commentators have argued that the problem has less to do with guns and more to do with civil liberties.

Speaking after the massacre at Virginia Tech in 2007, Richard Arum, Professor of sociology and education at New York University, remarked that Americans enjoy a right to privacy, a right to free speech and a right to due process that is extended to students in schools and colleges, including individuals who are mentally impaired.

"Unfortunately, these freedoms make it very difficult for schools to respond to individual troubled youth. Here was a case of a college student [Cho Seung-hui] who was very deeply troubled, but the school, because it was concerned about the youth's individual rights, had a very difficult time responding in common sense ways to the needs he'd expressed."

Challenged as to whether America's gun culture was to blame, Professor Arum was unapologetic: "Guns have been widely available in our society for a long time, and we didn't have this history of rampage school shootings."

He agreed, however, that when an individual with a history of mental illness was able to walk into a store and purchase a weapon, as Cho Seung-hui did, matters had got out of hand.

"It would be hard to argue that this makes any rational sense at all," he said.

Lethal lessons: Past killings

1974: December 30 New York, Olean, Olean High School – three killed

1986: December 4 Montana, Lewistown, Fergus High School – one killed

1987: March 2 Missouri, DeKalb, DeKalb High School – two killed

1992: May 1 California, Olivehurst, Lindhurst High School – four killed

1992: December 14 Massachusetts, Great Barrington, Bard College – two killed

1994: May 26 Kentucky, Union, Ryle High School – four killed

1994: October 12 North Carolina, Greensboro, Grimsley High School – one killed

1996: February 2 Washington, Moses Lake, Frontier Junior High School – three killed

1997: February 19 Alaska, Bethel, Bethel Regional High School – two killed

1997: October 1 Mississippi, Pearl, Pearl High School – three killed

1997: December 1 Kentucky, Paducah, Heath High School – three killed

1998: March 24 Arkansas, Jonesboro, Westside Middle School – five killed

1999: April 20 Colorado, Jefferson County, Littleton, Columbine High School – 15 killed

2005: March 21 Minnesota, Red Lake Native American Reservation, Red Lake High School – 10 killed

2007: April 16 Virginia, Blacksburg, Virginia Tech – 33 killed