An Ohio schoolboy was chased by a black clad man wearing a clown mask and wielding a knife.
The 14-year-old boy was able to escape by hurling a rock at the attacker and running to a bus stop, NBC reported.
When he arrived at the school the boy told teachers about the incident, who reported it to police.
Officers have been conducting inquiries in the area of Columbus where the attack took place. No arrests have yet been made, police said.
"We don't know whether this was a prank or not, but we are taking it seriously," Columbus police spokeswoman Denise Alex-Bouzounis said.
It comes after reports of multiple incidents of people dressed as menacing clowns attempting to lure children to an abandoned house behind a residential complex in Greenville, South Carolina. Greenville County Sheriff's Office had extra officers patrolling in and around the Fleetwood Manor apartment complex where the incidents allegedly took place.
Alex-Bouzounis said police in Columbus were aware of reports of the incidents in Greenville, but were concentrating on investigating the attack locally.