April 20 Is Also the Anniversary of Columbine...

What is it about this week in April? I just found out that not only is today the 15th anniversary of the Oklahoma City bombing, but that tomorrow is the 10-year anniversary of the school shooting at Columbine. April 19 also is the anniversary of the Waco siege and April 20 happens to be Adolph Hitler's birthday. Because of the historic significant of April 20, the Anti-Defamation League says radicals and extremists tend to plan events for that day, although, law enforcement officials aren't aware of any threats tomorrow, according to this news report.

Eleven years ago tomorrow, two very disturbed teenagers walked into Columbine High School, shooting 21 students and taking the lives of 13 people, before committing suicide. It is commonly said to be at the time the deadliest school shooting in U.S. history. Technically it was, but that's not counting a bombing at a school in Bath, Michigan in 1927 that claimed the lives of 45 people. Click here and here for more information.

For more information about the Columbine massacre, visit this commemorative Web site and this ABC News slideshow.