Jacob Abraham, 28, was hospitalized earlier this month. He was taken to hospice care last week and died on Monday, the attorney general's office said.
Abraham was arrested in November in Lowell, Massachusetts, just south of the state line. He was accused of killing 71-year-old Cynthia Toupin, his grandmother.
Authorities said Toupin died in Nashua following blunt force trauma to her head and/or a puncture wound to her neck.
The attorney general's office said it is no longer prosecuting the case.