The killings at a university in the state of Virginia have sparked yet again a heated debate about gun control in the United States. The BBC News website looks at some of the issues arising from the worst shooting spree in the country's peacetime history.
Why are shootings at educational institutions so common in the US?
This depends on who you ask. For those opposed to the country's liberal gun laws the key problem is easy access to highly powered weapons. They say the school shootings merely throw into sharp relief what is happening across a country where 30,000 people die of gun wounds every year. Others contend that these killings take place within a deep culture of violence, which they say is promoted in the US through music, film and video games.
But there are those who argue these incidents take place not because there are too many guns, but because there are not enough. "All the school shootings that have ended abruptly in the
last 10 years were stopped because a law-abiding citizen - a
potential victim - had a gun," said Larry Pratt, executive
director of Gun Owners of America. "The latest school shooting at Virginia Tech demands an
immediate end to the gun-free zone law which leaves the
nation's schools at the mercy of madmen."
Others argue that schools and colleges are not sufficiently protected, and that the lack of security is tantamount to an open invitation.
Have gun controls been tightened after previous incidents?
After the Columbine High School shootings in Colorado in
1999 more than 15 state legislatures passed gun control bills or dropped liberalisation bills supported by the National Rifle Association (NRA).
Nonetheless, in many cases these simply restricted the number or type of guns which could be bought. California for instance limited gun sales to one handgun per customer per month and outlawed some assault weapons.
And at the federal level, little changed. Following the Columbine killings President Bill Clinton proposed tougher legislation including raising the legal age of possession to 21 and closing loopholes on sales without background checks.
But they proved intensely controversial, and by the time the bill was to be voted on by Congress the president himself denounced it as so watered down it was "worse than current law".
Mr Clinton did however introduce the Assault Weapons Ban, a 10-year ban on 19 types of semi-automatic weapon. The ban expired in 2004 under President George Bush and has not yet been renewed.
What is security like at US institutions?
Some educational institutes, both high schools and colleges, have metal detectors at the entrance to stop guns being brought on site. But this is easier to do at institutions which are self-contained, and harder on universities which are spread out on campuses and have many points of entry.
What is the public view on gun laws?
The right to bear arms in America is seen as an important civil liberty, and the debate concerns how far to impose restrictions on that right. Politically, most Democrats favour tighter gun laws whilst the majority of Republicans are opposed to any new legislation, saying the problem lies in the lax enforcement of existing laws.
According to the Pew Charitable Trust, support for greater restrictions has slipped in recent years among the general public. A recent poll for the organisation suggested that 52% of people had favourable views on the NRA compared to 32% who did not.
In a separate poll in October last year, some 56% of people did however tell Gallup that they wanted stricter laws. However, when given the choice in that poll between enforcing current gun laws or passing new gun laws in addition to enforcing the existing ones, most people preferred simple enforcement.
How does the US compare with other countries around the world?
Accurate figures on firearms are scarce, but there are an estimated 200 million guns in circulation in the US, a country with a population of about 300 million.
According to a Harris poll conducted in 2001, approximately 39% of all American households own at least one gun.
The risk of being killed by a firearm in the US is higher than in any other Western nation. Of countries outside war zones, the risk is greatest in South Africa, according to a United Nations report.
There are no recent statistics available but UN figures from 2000 showed for every 10,000 Americans, 0.3 were killed by firearms, compared with 0.01 in the UK where handgun ownership was banned in 1997.
In Switzerland where every man of military age is required to keep a gun at home as part of the country's civil defence policy, the number of deaths per 10,000 population was 0.05.
In South Africa it was 7.1 for every 10,000 people.