A graphic video's been posted on social media showing an elderly woman's skull being fractured.
Newry and Mourne PSNI did it to highlight the dangers of stoning passing vehicles.
They say it happens on a regular basis in Newry.
In the post, an officer wrote "It doesn't have to be a brick to cause serious damage or injury,
"A stone and the fact the vehicle is moving adds to the dangers."
Search operation under way after reports of man going overboard from ferry
Sentencing Bill, including Charlotte’s Law, to be introduced shortly: Naomi Long
Man dies following crash between car and van in Hillsborough
Woman dies in Cookstown road crash
Extra £400m to support health and education in Northern Ireland