Was the Boston massacre timed to coincide with what some are calling "Devil Week?"
Many are wondering if the date of the bombings might provide an important clue.
Six years ago, 33 people were killed in the Virginia Tech massacre when a mentally disturbed student opened fire.
14 years ago, on April 20, 1999, 13 people were gunned down at Columbine High School. Four years earlier, on April 19, 1995, Timothy McVeigh blew up a federal office Alfred building in Oklahoma City, killing 168 people.
On April 19, 1993, the FBI raid in Waco, Texas, ended in tragedy when fire broke out at the Branch Davidian compound, leaving 90 dead.
There is one other event of note that makes people call this devil week. That is the birth, on April 20, of the ultimate devil himself, Adolf Hitler.
Now, another dark day falls in a week that has seen so much tragedy.