First part of this is about bomb technical issues.
Same to some extent as:
Van D. Romero New Mexico Tech
Smoke is white, indicating gunpowder explosion. Consistent with pressure cooker bombs.
Ignition is the complicated step.
First one goes off, second person can set off second. So close together in time is not so hard
Roof of 6 story hotel nearby find a lid of pressure cooker.
William B Evans supt Boston police.