Police say a man walked onto an Ohio school playground during recess and stabbed an 8-year-old girl, who's now in critical condition.

Police are searching for the man after the attack on the second-grader Friday at World of Wonder school in Dayton.

The Dayton Daily News reports that the school secretary who called 911 said a man had stabbed someone on the playground.

Police described the suspect as a black man estimated to be 18 to 20 years old, a little less than 6 feet tall, wearing athletic shorts and a beige or green sweatshirt over an orange shirt.

WDTN-TV reports investigators said they didn't know why the girl was attacked.

The school was put on lockdown, then dismissed for the day.