Residential Housing...

The big story in Western Pennsylvania today is that the "Capitol Police" have come to the Pittsburgh Suburb of Penn Hills to investigate "threatened harm allegations" involving
tresspassing on US Senator Rick Santorum's "home state residence house".
Some in the Pittsburgh area claim that Santorum's house is a sham, that it has only two bedrooms (the Santorums have six children), that the Senator hasn't lived in it since he was elected to the Senate and that Santorum's real residence is a million dollar home he owns in Leesburg, Virginia.
To some locals the house has always been a point of contention, Democrat Party activists have always made this complaint although I'm certain that many Dem Senators and Congressmen own residences in Virginia or Maryland where they really reside. My mom asserts that the Santorum "in laws" live in a large home on an adjacent Penn Hills property.
The property was also prominent in the news this past year when it was learned that 5 of the Santorum children were enrolled in a Pennsylvania Cyber School at Penn Hills School District taxpayer expense. Senator Santorum has since withdrawn his children from the cyber school.
Why "The Capitol Police"?
Created by Congress in 1828, the original duty of the United States Capitol Police was to provide security for the United States Capitol Building. Today their mission has expanded to provide the Congressional community and its visitors with the highest quality of a full range of police services. These services are provided through the use of a variety of specialty support units, a network of foot and vehicular patrols, and fixed posts.

Today's United States Capitol Police Officer has the primary responsibility for protecting life and property; preventing, detecting, and investigating criminal acts; and enforcing traffic regulations throughout a large complex of congressional buildings, parks, and thoroughfares. Additionally, the protection of Members of Congress, Officers of Congress, and their families is expanded by statute to the entire United States, its territories and possessions, and the District of Columbia.

So the Capitol Police serve a similar function for members of both houses of Congress as the Secret Service does for the President and visiting foreign leaders.
A local news report recently stated that a "Casey operative" had peered in the windows of the "residence" (and reported there were no curtains and no furniture) and that allegation is the basis of the investigation.
Bob Casey is the Democrat Candidate who will be opposing Santorum for the Senate in November. He has denied that any member of his campaign is involved in this matter.