The Hastings Police Department says the incident occurred at Alcott Elementary.
According to police, the suspect pulled out a knife after the victim asked the boy if he wanted to trade bikes. The suspect was riding a black bike with black rims.
The suspect reportedly held the knife against the victim's shin after asking if he "wanted the sharp end." A friend of the suspect told him to put the knife away and the two then left the area.
The suspect is described as a white male with blond hair, about five feet tall, wearing a gray or silver shirt and shorts. The friend is said to have glasses and was riding a red mountain bike. Both appeared to be around 11 years old.
Officers still looking for the two boys.