FORT ANN — A 50-year-old man is accused of strangling his 95-year-old grandmother to death Sunday night, the Washington County Sheriff's Office said Wednesday.Leona Twiss was found dead inside a home, located at 9 Twiss Road in Fort Ann, at 11:30 p.m. July 9 and investigators determined she was killed by her grandson, Kevin Gonyea, the sheriff's office said.