The Senate will join in a moment of silence at 2:50 p.m. Monday to mark the exact time that the first bomb exploded last week near the finish line of the Boston Marathon.

Senate aides said the decision was made Monday to join in an official observance of the attacks that is expected to bring Boston, and most of Massachusetts, to a standstill Monday afternoon. Several Boston-area radio stations plan to go silent at that time, while churches will ring bells in observance of the victims and survivors.

President Obama also plans to observe the moment of silence at the White House, aides said Monday.