Massachusetts authorities were in the process of securing an arrest warrant charging former priest Richard D. Lavigne with murder over the 1972 slaying of 13-year-old altar boy Danny Croteau when Lavigne died suddenly last Friday. His death came the same day detectives were set to ask a magistrate judge to sign off on the plan, said Hampden District Attorney Anthony D. Gulluni. Lavigne, who was defrocked in 2004, was a predator who molested scores of children across numerous parishes in Western Massachusetts from the 1960s until 1991, when the church removed him from a public role. Gulluni pointed to new evidence incriminating Lavigne in the five-decade-old crime, including hours of recent interviews and a letter he wrote that was examined by a forensic linguist. “We were prepared to then prosecute Richard Lavigne and prove his guilt beyond a reasonable doubt,” Gulluni said. Gulluni said Lavigne, 80, was “not well,” but did not specify a cause of death. Lavigne reportedly admitted his guilt to a Massachusetts state trooper earlier this year, saying in an interview that he beat Croteau and left the boy by a river in Chicopee, Massachusetts, in April 1972, then found the child floating face down when he returned to the scene later. Still, Lavigne continued to insist that he did not kill Croteau.