"Two kids, who are unaccompanied, and they've been walking around for probably around 20 minutes by themselves," the man said.
The caller then tries to guess the children's age as "7 or 8" for the boy and "about 6" for the girl. He said the children had asked to pet his dog and he was concerned that no parents or guardians were with them.
The caller eventually flagged down police who made contact with the children in a Silver Spring park before calling in state Child Protective Services.
The children were later identified as the 6-year-old daughter and 10-year-old son of Danielle and Alexander Meitiv, who encourage their children to explore their independence.
But Maryland law says that children under the age of 8 must be in the care of a person at least 13, according to Child Protective Services.
The children's parents were later contacted by Child Protective Services after officials had taken custody of the children, returning them to their parents after several hours.
Danielle Meitiv has declined to comment but posted on Facebook earlier this week that “police coerced our children into the back of a patrol car, telling them they would drive them home. They kept the kids trapped there for three hours, without notifying us, before dropping them at the Crisis Center, and holding them there without dinner for another two and a half hours."
“We finally got home at 11 pm and the kids slept in our room because we were all exhausted and terrified," she wrote.
No charges have been filed, but police said the investigation is still ongoing.
The family attorney, Matthew Dowd, said in a statement: "The Meitivs are rightfully outraged.”
He added: "We must ask ourselves how we reached the point where a parent’s biggest fear is that government officials will literally seize our children off the streets as they walk in our neighborhood. The Meitivs intend to fully vindicate their rights as parents and to prevent this from happening to their children again."
This is not the first time that the Meitvs' practice of "free-range" parenting has gotten them in trouble with authorities. The couple were "found responsible for unsubstantiated child neglect" by state Child Protective Services earlier this year, after they allowed their children to walk home alone from a neighborhood park about one mile from their home.
No criminal charges were filed and a Maryland State Department of Human Resources spokeswoman would only say at the time that the case would serve as "a point of reference that will be used in any future decision."