During three days in 2001, Sampson killed three strangers - retiree Philip McCloskey in Marshfield, Massachusetts, college student Jonathan Rizzo in Abington, Massachusetts, and Robert Whitney in Meredith, New Hampshire. He also attempted to kill a fourth victim and stranger, William Gregory, in Vermont. Sampson killed McCloskey and Rizzo after they picked him up hitch-hiking, beating them to death. Shortly after that he strangled Whitney. Sampson pleaded guilty to the three killings on September 9, 2003, and was sentenced to death on December 23, 2003, by a federal jury in Massachusetts. He received the death penalty for the two Massachusetts killings, and a life sentence for the New Hampshire case.