More than 100 people were killed in a massacre in one of the poorest neighborhoods of Haiti’s capital, a leading human rights group said on Sunday, describing the killings as the personal vendetta of a gang boss who had been told that witchcraft caused his son’s fatal illness.

At least 110 people were killed in the slaughter, which began on Friday in the Wharf Jeremie section of Cité Soleil, a sprawling slum in Port-au-Prince, according to the National Human Rights Defense Network, a civil rights group based in the capital. Older people who practiced voodoo appeared to have been targeted, according to the group. That assessment was backed by another rights organization and a Cité Soleil resident.

Haiti has been convulsed by violence since early this year, when rival gangs banded together in an attack on government institutions, including police stations, prisons and hospitals.

This is a developing story.