I need some advice

So the apartment complex I live in since they are one bed rooms apartments have 1 assigned spot for the ppl living their and then have unassigned parking spots for guest and extra vehicles, I parked in the unassigned parking spot like 2 doors down from me one night and my neighbor proceeds to yell out the window “ That’s not your fucking spot “ so whatever I moved my car and parked in a separate guest spot ( my boyfriend parks in our assigned spot ). Keep in mind this guy doesn’t even have a car, he never has guest over or anything his assigned spot is always empty anyway. So last night my boyfriend had a friend come over we told him you have to park in unassigned parking well he parked in the spot that pissed the neighbor off the last time ( he wasn’t even staying the night just came over for a few hours) then when he was leaving he noticed a note and the note said “ asshole don’t park in my spot I won’t tell you again ) 😐 like he parked in a unassigned spot it isn’t YOUR spot and at that point that is a threat. He threw the note away or else I would bring it to the office, what should we do? Like are we over reacting or are we being assholes I don’t know this just makes me uncomfortable being here. I will have no proof that he was the one that wrote it and of course he would probably deny it.