Police in Banbridge have urged people to "wise up" after a large stone was thrown towards a primary school.
The stone "like a large lump of granite" was hurled towards the front of Dromore Central Primary School in Co Down.
No child was hurt in the cident but a car was damaged after being hit by the stone.
A PSNI spokesperson said that the incident could have been much worse.
"We're investigating a quite concerning incident. On the face of it, a criminal damage, but we could today easily have been dealing with the death of a child," the spokesperson said.
"Central Primary School, Dromore. Yesterday afternoon, as the school was getting out, a large stone, described by one of our guys who attended as "like a large lump of granite", was hurled from one of the nearby streets towards the front of the school. Thankfully, it was only a car that was hit.
"Whilst there is damage to the car, damage which the perpetrator should be held fully to account for, it could have been much worse. Had something that size hit a child, the injuries could have been horrific. If it had hit a younger child in a pram, it would almost certainly have been fatal."
Police appealed for anyone with information to come forward before a child was seriously hurt.
"Whatever the reason, whatever the motive, this is completely unacceptable. If you know who this was, we need to get speaking to them. If there are unresolved issues, we need to get it nailed on the head before we have a repeat, as the consequences of that sort of carry on near a primary school do not bear thinking about," the spokesperson said.
"You can call us on 101, or pass on any information completely anonymously via Crimestoppers on 0800 555 111. The incident number is 877 of yesterday, 15/05/18.
"If that was you who threw the rock, stop and think. You could be sat at home now waiting for your front door to come in round you as we investigate the death of a child. That isn't the sort of reckless act which leaves you. Wise up."