What is it about April and homegrown terror?

No one can forget that the 2001 terror attacks on the World Trade Center occurred in September.

But less remembered, perhaps, are that other domestic-related attacks occurred in April, near or on Patriot’s Day, including what appears to be another terror attack on Monday in Boston.

Though Monday was April 15, Patriot’s Day was being celebrated in the city during the Boston Marathon. Patriot’s Day commemorates the Battles of Lexington and Concord on April 19, 1775 - a trigger in the American Revolution.

The following list is of incidents that fell on, or near, Patriot’s Day - but only coincidentally. And, of course, many other tragic events occurred through many other dates in history.

April 19, 1993. Agents from the Bureau of Alcohol, Tobacco and Firearms laid siege to a compound in Waco, Texas held by David Koresh, leader of the Branch Davidians religious group. The group had been holed-up at the compound for 50 days after a February gun battle in which four agents and six Branch Davidian members were killed. A fire from the April 19 siege destroyed the compound, killing 76 people inside, including Koresh.

April 19, 1995. Oklahoma City bombing of the Alfred P. Murrah Federal Building, in which 168 people died, including 19 children. Timothy McVeigh was found guilty of the attack and was put to death in 2001. Terry Nichols remains in prison as a co-conspirator. McVeigh cited Waco as one of his reasons.

April 20, 1999. Two students set out on a murderous rampage at Columbine High School in Colorado, the first horrifying mass attack at an American school. Eric Harris and Dylan Klebold, armed with firearms and bombs, ended up killing 12 students and a teacher. A score were injured before the two boys killed themselves, and set off a national debate on gun control.

April 16, 2007. A lone gunman, Seung-Hui Cho, set off heavily armed across the campus of Virginia Polytechnic Institute, known better as Virginia Tech. The senior killed 32 and wounded 17 in two attacks, then killed himself.

April 15, 2013. Two bombs explode near the finish line of the Boston Marathon, killing three, and seriously injuring many others.