A long-standing element of ufo/paranormal conspiracy theory, cattle mutilation has been reported in the United States for several decades. Here's some FOIA documents relating to the FBI's investigation (and discussions of whether they had jurisdiction to investigate) from the 1970's. All links are PDFs: cattle1.pdf, cattle2.pdf. cattle3.pdf, cattle4.pdf,cattle5.pdf.
The May 2009 issue of the FBI Law Enforcement Bulletin has a special focus: "Beyond Survival," helping law enforcement officers to do more than survive in their careers. [more inside]