Here's a secret for you - and really keep this one quiet - letter mail addressed to folks on the House and Senate side is actually examined for bombs and sometimes x-rayed for content in a separate facility long before it goes into any of those office buildings.
There, now you know the secret.
This business of "attacking a building" must also account for all the other buildings through which those letters traveled. For example there's the Brentwood facility. Maybe somebody wished to shut it down and make it's records inaccessible to investigative personnel?!?!?!?
...I have also seen reports that the ONE thing BILL CLINTON wants to disappear from Washington D.C. is the Impeachment Evidence against him stored in the FORD Senate Office Building, especially the Evidence of his XX Violent Rape of JUANITTA BRODERICK.
...We have yet to see the last Attacks on OUR Ford Senate Office Building.