What threatening behavior did Mr. Keller display?

Mr. Keller displayed threatening behavior by directly threatening the Hyundai driver. This suggests an aggressive or confrontational stance towards the individual, which could escalate tensions and create a potentially dangerous situation. Threatening someone typically implies a verbal or physical menace that could intimidate the person being threatened.

In this context, it is important to recognize that simply intending to report someone or stating one might leave the scene does not imply a direct threat to the individual's safety. Similarly, threatening to involve the fire department does not constitute a personal threat but instead might signal a concern for safety or compliance with protocols. Thus, Mr. Keller's direct threat targets the Hyundai driver specifically, marking it as the most significant and alarming behavior in this scenario.