The suspected man is a brother of the dead six-year-old girl while the other two victims were also sisters who belong to Newark, New Jersey, they were the daughters of the suspected man' mothers' relatives.
"Hug you all's loved ones tonight", according to a video message from the mother.
"I wear a uniform, but I am a father", Velez said. "Tomorrow is not guaranteed..."
Kelley called the police who pronounced them dead at the scene. A 2-year-old - another one of the suspect's sisters - was in the home at the time, but was unharmed.
The Latest on the slayings of three children in a home outside Washington, D.C.
Williams faces charges of first-degree and second-degree murder, along with related charges.
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Insurers have already cited uncertainty surrounding the funding as a reason for big premium increases for 2018. At total of 360,000 Virginians bought health insurance this year through individual plans , Treanor said .
Williams is being held without bond.
Donelan tried to calm local parents, saying, "We believe that this [crime] is confined to this particular home".
"This is one of the the most hard scenes that our officers arrived on", Donelan said, adding that the neighborhood where the children were found was quiet.
More family members of the victims are being contacted. The three girls were found stabbed in their beds.
First responders and investigators have been offered counselling following the traumatic discovery.
That work is being done in concert with the office of State's Attorney Angela Alsobrooks, who took the opportunity to speak on behalf of county residents, saying, "We are absolutely heartbroken and we are so absolutely devastated".