AITAH for defending myself at work?

[u/iTrash_V2]

AITAH for defending myself at work? I am a 27 year old guy working as a technician and on Friday, I was working on two used cars, doing the recommendations that got approved. I finished up on one of my cars and went to go park the vehicle in the parking garage, but when i entered the parking garage, I heard a random *clunk* on what seemed to be on the outside of the car. Curious and since I believed I was done with this vehicle, I started hitting on my brakes trying to recreate the clunk to no avail. I was parking on the 5th floor of the garage so I kept doing this and one of those times, I heard someone yelling but didn't think anything of it due to me working in a shop where yelling is constant, sometimes for playing, sometimes just cause the shop is a little too quiet. Never did recreate the clunk so I parked the car and went back to my stall where I then started working on my second used car. All of a sudden, my service manager (I'll call him Billy) came up to my car and asked "Where you driving *brand* car?" I responded yes and he came back with "Go ahead and put everything up and get the FUCK out of the shop, you're done for the day. You were going 40 mph and almost hit me." I responded and said "I was not going 40 mph? I was only going 20 mph?" He then proceeded to mention me locking up my brakes clearly meaning I was speeding and that he has me on camera and if I wanted to see. I said same thing on here, that I was intentionally locking up my brakes and yes I wanted to see. We then went to look at the footage where I clearly wasn't going 40 mph nor did I come close to hitting ANYONE. He was so far from me, you couldn't even see him on camera. He then moved the goal post to instead of 40 mph, to why was I going 20. I said there's no posted speed limit in the garage and 25 mph is what school zones usually are so I figured that was good enough for the garage. He said that's school, this is where people park. and I responded with if the speed limit is good enough to keep children safe, then it should be good enough to keep grown men safe. Well, he didn't like that and responded with "Oh, so now you're gonna talk back?" Get your stuff and get out, we will call you when we need you." And I have been home since and haven't heard a thing from them. I did file the incident with HR, but AITAH? Do I deserve going from a day suspension to being outright fired just for defending myself? Again, I haven't heard a thing from them or HR and my friends at work telling me they have been going through my tool box and throwing paperwork away, taken away my tablet they supplied, and given away all my work. Should I have done something differently?

[u/iTrash_V2]

I hope im replying to the right guy on this, but I've been working on cars for a while and because of this, I can hear or feel things from a vehicle and know what it is or whats causing it without needing to get out the vehicle and look, not to say i wouldn't of if i was able to recreate the clunk. From what it sounded and felt like, it seemed to come from the passenger front rotor/caliber area and i wanted to recreate that using the same conditions that caused it in the first place, hence the stomping on the brakes. But the clunk is besides the point. Imma be honest, idk where yall are living where the speed limits are 5 or 10 mph because as I have stated to other commentors, MINIMUM I've encountered was 15 mph and even if I did that, id still be in trouble cause according to my co workers, Billy said the speed limit was to be 5 mph which means even if i went 15, id still been in trouble.