WILKES-BARRE, Pa. (AP) -- Two half-brothers have pleaded guilty to murder charges in the drug-related slayings of three people in northeastern Pennsylvania last year. In Luzerne County Court on Friday, 19-year-old Shawn Hamilton pleaded guilty to three counts of first-degree murder and 17-year-old Sawud Davis pleaded guilty to three counts of third-degree murder. The shootings in July 2012 in Plymouth claimed the lives of 21-year-old Bradley Swartwood, 17-year-old Nicholas Maldonado and 15-year-old Lisa Abaunza. Prosecutors said the men shot the victims because they didn't want to leave witnesses to a drug deal. Hamilton also pleaded guilty Friday to first-degree murder for mortally wounding another man in Wilkes-Barre the day before the triple shooting. Twenty-two-year-old Kenyatta Hughston died three months after being shot in the head in what authorities said was also a drug-related incident.