Three kids under the age of 10 were killed in a house fire while visiting their grandfather on Saturday.
The Clark brothers were staying with their relative in Arcadia, Florida, when tragedy struck.
The grandfather was pulled from the home by an unknown hero, and is recovering at a nearby hospital.
"It's unthinkable, you know? I can't imagine what it would be like if my children died in a fire," a neighbor told WITI.
A 911 call made around 4:30 a.m.led investigators to believe that foul play was involved.
49-year-old Marian Evette Williams was taken into custody after the incident. Relatives said she is an ex-girlfriend of the grandfather of the deceased children.
According to WITI, Williams has a violent past, including a recent incident. She was arrested the day before for battery and burglary.
Williams is being held in jail on no bond, and has been charged with three counts of first-degree murder.