Ohio is an "open carry" state. To put that simply, walking around a building with a firearm is not grounds for arrest, nor does it fulfill the requirement of reasonable suspicion for an investigative detention. So even if police were correct in their assumption that Crawford was carrying a firearm, which he was not, they still wouldn't have had grounds to question him about it, much less point their firearms at him.
"Openly carrying a firearm, by itself, is not illegal. The fact that someone has called 911 or flagged down an officer about seeing someone with a gun in public is probably not enough to support an investigative detention. In such situations, an officer must observe the subject and evaluate whether reasonable suspicion exists to justify detaining the individual. If the individual is doing nothing else that arouses suspicion, simply wearing a gun will not justify detention."