The murder in April 1999 of 13 people at a Colorado high school - by two heavily armed pupils - sent shockwaves across the US.
After their shooting spree, Eric Harris, 18, and Dylan Klebold, 17, killed themselves.
Here - using BBC Radio archive - we recall how events unfolded that day.
Photographs courtesy: AFP, Getty Images.
Slideshow by Paul Kerley. Publication date 20 April 2009.
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