Round About the Time the American Revolution Began
Given the time of year, round about the date the American Revolution began, and the preliminary description of what the bombs were constructed of, it is a good bet white guy loons are the folks who set off the bombs in Boston. This is the time of year white guy loons have set off some pretty big motherfucking bombs in the past.
Do not be surprised when more shit gets blown up. In fact, if I were an American living in a big urban centre and I had some vacation time in the bank I would be booking a trip to Mexico. Right fucking now.