A D.C. elementary school has tightened its afternoon dismissal policies after a three-year-old was allowed to leave campus and walk home without his mother’s knowledge.

His mother, Gwendolyn Green, said her son was nowhere to be found Wednesday afternoon when she tried to pick him up from C.W. Harris Elementary in Southeast Washington. School staff weren’t sure where he was, she said, as NBC News first reported.

Frantic, Green called her mother, with whom she shares a home, and learned that the boy had just walked through the door. He had made his way safely home from school, a total of three blocks.

But Green was irate. “Somebody could have just stole him and they wouldn’t have known who did it,” she said.

School system officials said the principal reviewed camera footage that showed the boy leaving the school with another student and that student’s older sibling.

“The school has updated the dismissal procedures to ensure this doesn’t happen again,” spokeswoman Melissa Salmanowitz wrote in an e-mail.

Under the updated policy, a parent or caregiver must sign out the student on a class roster at pick-up time.