The terrifying bomb attack at yesterday's Boston Marathon took place on Patriots' Day - a New England tradition that has been marred by tragedy.
Patriots' Day carries historical significance in the birth of America, marking the day that the 'shot heard 'round the world' was fired at the Battles of Lexington and Concord during the Revolutionary War.
But in recent years, it presents numerous grim anniversaries.
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Carnage: The terrifying bomb attack at Monday's Boston Marathon took place on Patriots' Day - a New England tradition that has been marred by tragedy
Bloodbath in Waco: The federal siege of the Branch Davidian compound, which left 82 members of the cult dead, ended on Patriots' Day in 1993
Patriots' Day is held in reverence by right-wing domestic groups, those who oppose the federal government and other mass killers who have chosen to strike on or around the third Monday in April.
The federal siege of the Branch Davidian compound, which left 82 members of the cult dead, ended on Patriots' Day in 1993.
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Seventy-four people, including Davidian leader David Koresh, perished in the facility following a shootout with federal agents and a massive fire.
The 1995 bombing of the Oklahoma City federal building, which killed 168, occurred the day after Patriots' Day. Bomber Timothy McVeigh was said to believe that the date was significant.
Devastation: The 1995 bombing of the Oklahoma City federal building, which killed 168, occurred the day after Patriots' Day
Killers: Eric Harris, left, and Dylan Klebold, right, murdered 12 fellow students and a teacher during their violent massacre at Columbine High School in 1999
Evil: Harris and Klebold's motives are not known, but it is believed that they picked the date because it was also Adolf Hitler's birthday
On April 20, 1999 - also a day after that year's Patriots' Day - Eric Harris and Dylan Klebold shot and killed 12 fellow students and a teacher during a murderous rampage at Columbine High School.
The motives of Harris and Klebold were never made clear, but it is widely believed that they were influenced by the Oklahoma City bombings and may have picked the date because it's also Adolf Hitler's birthday.
On April 16, 2007, Seung Hui-Cho killed 32 people on the Virginia Tech campus before turning a gun on himself in one of the deadliest school shootings of all time.
April 15 is also Tax Day, when federal income tax returns are due.
A look back at some of the worst bombings on US soil
Spree killer: On April 16, 2007 - which was also Patriots' Day, Seung Hui-Cho murdered 32 people on the Virginia Tech campus before turning a gun on himself in one of the deadliest school shootings of all time
In recent years, it has been seized on by members of the Tea Party as cause to protest federal government policies and tax rates.
A Justice Department source told MailOnline that authorities are looking into the possibility that the Boston attack, which killed three and injured 144 more at the finish line of the Boston Marathon, may have been planned to coincide with Patriots' Day.
President Obama himself acknowledged the significance of the holiday during his briefing hours after the bombing.
'Today is Patriots Day,' he said. 'A day that reflects the freedom Boston has celebrated throughout its history.'
Historic day: President Obama himself acknowledged the significance of Patriots' Day during his briefing hours after the Boston bombing