During MSNBC’s coverage of the Boston Marathon explosion, “Hardall” host Chris Matthews and Democratic Massachusetts Rep. William Keating speculated on what may have motivated the bombing.

Keating pointed out that it could be related to Tax Day.

“Now, we have an international event, the marathon, the oldest marathon,” Keating said. “And we also have Tax Day, April 15, so we don’t know if that’s the kind of symbol a domestic terrorist might use as well. So there’s a lot that’s not known, but we’re beginning to get a lot of information that will be shared with the public for their own safety. But a word of caution to everyone to just to really be careful.”

Matthews remarked on the Tax Day suggestion, saying that it sometimes causes emotions “in the wrong parts of the brain.”

“Well you’re right, congressman,” Matthews replied. “So many iconic days — it’s Patriots Day, it’s the Marathon Day, it’s the Kennedy Library always up there. And also as you point out — I just forgot because I filed already — that it’s filing day for the federal income tax, which does cause some emotions around the country, sometimes in the wrong parts of the brain.”

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