People have been talking about this week in April for years, but last year two more tragedies were added to the list. April 15th marks one year since pressure cooker bombs exploded near the finish line of the Boston Marathon, killing three people and injuring more than 250 others.

On April 15, 1912, the Titanic sank, killing more than 1,500 people and Abraham Lincoln was assassinated the same day in 1865.

In 2007 on April 16th, a student at Virginia Tech killed 32 people and wounded 17 others before taking his own life in a campus shooting. It's the deadliest shooting by a gunman acting on his own in United States history.

Also last year, on April 17th, a fertilizer plant in West, Texas exploded, killing 15 people, injuring more than 160 others, and damaging 150 buildings in the area. Investigators still don't know what caused it.

On April 19,1993, authorities raided a religious compound in Waco, Texas. After a tear gas attack, gun battle, and a fire, 76 men, women and children and four ATF agents died.

Two years later on April 19, 1995, Timothy McVeigh and his accomplices chose the same day in an act of revenge to blow up a moving truck in front of a federal building in Oklahoma City. The bombing killed 168 people, and injured more than 680 others.

On April 20, 1999, two Columbine high school seniors murdered 12 students and one teacher, and injured 27 others. They also planted explosive devices that never detonated. The pair, who took their own lives in the event, wrote in journals they wanted their actions to rival the Oklahoma City bombing.

Finally, April 20, 2010, an explosion on the Deepwater Horizon drilling rig in the Gulf of Mexico killed eleven workers and injured 16 others. It created the largest oil spill and environmental disaster in U.S. history.