CHICAGO (CBS)--A student at Maine South High School in Park Ridge has been arrested after allegedly making a threat against the school, police said.

The 18-year-old student, Saul Merino of Norridge, allegedly posted a photo on Snapchat of someone holding a rifle.

(Park Ridge Police)

The photo’s caption read, “No one come to school tomorrow,” according to police.

A Maine South student saw the photo and told his parents, who then called police.

An investigation determined the photo was a prank, but that it had indeed been posted by Merino, police said.

Merino was charged with felony disorderly conduct.