The fact that he flagged down a cop to tell them about it makes it pretty clear that he wasn’t really looking to drug them per se, but rather to cause a legal incident. It may be that he wanted to sue Dairy Queen for profit, or perhaps get someone at the DQ store in trouble, or to blame it on a political group he deems undesirable (immigrant workers, trans people, liberals, etc.). In any event, it’s psychopathic.