Police in Coonabarabran, NSW, have arrested 66-year-old Kathleen Heggs for the alleged murder of her grandsons, Max Johnson, 7, and Sam Johnson, 6. The boys were found dead in separate rooms of their home.

Authorities were alerted after a disturbing message was sent to the Department of Communities and Justice. When officers forced entry, Heggs reportedly tried to harm herself.

She has been charged with two counts of murder and was denied bail. Heggs is scheduled to appear at Parramatta Bail Court.

The children had been living with their grandmother for 11 months before the tragedy. NSW Premier Chris Minns called the incident “incomprehensible.”

Police believe no one else was involved and there is no ongoing threat to the public. A candlelight vigil will be held at Neilson Park to honor the boys.

Assistant Commissioner Brett Holland said the deaths have shocked the small town and described the situation as “devastating.”