Police say 49-year-old Bridget Erwat was taken into custody after a passerby noticed a 4-year-old and an 8-month-old in her car in a Costco parking lot in Melville just after 2 p.m.
The Good Samaritan unlocked a door through an open window and took the children into the store for safety.
It appears that the girls were in the unattended vehicle a minimum of 10 minutes before they were found.
Erwat runs the child-care center Bridget's Children's Place out of her Amityville home.
She is charged with endangering the welfare of a child.
Neither girl was hurt.
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