More April 2nd events.. The American entry into WW1 is the most significant.

1982 – Falklands War: Argentina invades the Falkland Islands.
1992 – Forty-two civilians are massacred in the town of Bijeljina in Bosnia and Herzegovina.
2012 – A mass shooting at Oikos University in California leaves seven people dead and three injured.[2]
2014 – A spree shooting occurs at the Fort Hood army base in Texas, with four dead, including the gunman, and 16 others injured.
2015 – Gunmen attack Garissa University College in Kenya, killing at least 148 people and wounding 79 others.