Columbine killing took 16 minutes

Harris and Klebold planned to blow up the cafeteria

It took 16 minutes for two teenage gunmen to commit the deadliest school shooting in US history, a police report has revealed.

The full report into the Columbine High School massacre details the events of 20 April last year, when Eric Harris and Dylan Klebold killed 12 students and a teacher before killing themselves.

Police has been criticised for being "too slow"

The detailed minute-by-minute account also sheds new light on the police operation, which the victims' families say was too slow.

The 700-page document appears to contradict claims that the police officers could have saved lives had they acted more quickly.

But it also confirms that poor knowledge of the building and uncertainty over the number of gunmen meant the police took four hours to reach the teacher who died and 23 other people injured during the shootings.

The report has been published on a CD Rom as well as in written form and is based on about 5,000 witness interviews and 10,000 pieces of evidence.

Many of the details, including video clips of the massacre, have already been published or broadcast.

Detailed account

A timeline explains the exact sequence of events from the moment when Harris and Klebold arrived in their cars at 11.10am.

The massacre was the deadliest shool shooting in US history

According to the report, they shot their victims after their home-made bombs in the school cafeteria failed to detonate.

Had their bombs worked, authorities believe the number of victims would have much higher - there were 488 people in the cafeteria at the time of the attack.

The document also illustrates the problems the Swat teams had in entering and clearing the building.

The first team of six officers got into the school at 12.06, two minutes before Harris and Klebold shot themselves in the head in the library.

But they had no ground plan of the building and thought the cafeteria was where it had been four years previously. They had to check each room before moving on.

They could not get clear directions to the science area, where the teacher lay dying. They eventually reached him too late.

The library, where most of the killings took place, was reached at 15.22 - more than four hours after the shootings started.

Calls for gun control

The Columbine massacre and a series of other recent shootings in the United States prompted public demands for stricter gun control laws.

Clinton wants tighter gun control laws

Tens of thousands of women joined the Million Mom March in Washington and more than 60 other US cities on Monday, urging the American Congress to act on the issue.

President Bill Clinton and his wife, Hillary, joined the protesters and addressed mothers at a reception organised at the White House.

Twelve children die of gunshot wounds every day in the United States.