On December 29, 1999, Park Police officers and investigators conducted an investigation of an accident at Arlington National Cemetery in which a 20-year-old contract worker was fatally injured.  Although the cemetery is under the jurisdiction of the Army, the Park Police investigate accidents and criminal activities under an interagency agreement.  The victim was driving an ATV which was pulling a trailer with a dozen headstones, each weighing 208 pounds.  He was driving down a hill in the sleet and rain when he lost control of the vehicle and attempted to jump off.  His clothing got caught on the vehicle, though, and he was subsequently pinned against a tree by the ATV and its cargo.