(Newser) – A 7-year-old girl was hospitalized Friday afternoon after being stabbed by a man on her school's playground, CNN reports. The victim, a second grader at World of Wonder School in Dayton, Ohio, suffered serious injuries. "It's sickening," a woman present at the school during the attack tells WRGT. "It's heartbreaking, and I don't understand why someone would come and do that to a second grader." The attacker was not apprehended. Police say they aren't sure why the girl was stabbed or if she was specifically targeted. But school employees tell WHIO police "have a very clear and strong lead" on a suspect. World of Wonder was locked down following the stabbing, and the school plans on having additional security when children are playing outside in the future. (Read more stabbing stories.)