Whippet accused of biting

I live in the UK in a dog-friendly block of flats with my sweet whippet. We don't have concierge and have been struggling with people entering the building, behaving antisocially and stealing parcels. I was with my whippet, who was on a short leash, moving my neighbours' parcels to a safer area that requires fob key access. I noticed someone behaving seemingly erratically - walking quickly into the lift, coming back out again, going into the stair case and coming back out again. I didn't recognise him but he seemed to have a fob so I decided to leave it. While I was moving the parcels, he walked rapidly and unexpectedly through the doorway I was standing in. My whippet was startled and lunged at him, barking. He then doubled over, seemingly in agony, screaming. I tried to check on his wellbeing but he asked me to leave him alone. He looked really scared so I backed away. At this point, I still had no idea who he was and what he was doing in the building.

After some time has passed, I have just received an email from the management company claiming my dog bit a security guard and they are considering removing my dog. I immediately went to the security office, where I saw him. I asked him what had happened and he showed me a photo of what looked like a faint scratch (it did not look like a bite mark). A hole had been ripped in his trousers - I believe in the pocket area. He claimed he had muscle spasms and needed a shot. I am certain the spasms were due to stress because I can't see how they could have developed from a small scratch. He claims there is security footage but wouldn't show it to me - saying I should deal with the management company. He is clearly terrified of dogs and refuses to engage with me.

I have no idea what to do. I have contacted my insurance company and made an appointment with a behaviourist. I will have to wait until Monday to hear back from the management company. I am neurodivergent and my dog provides a huge amount of support with this. I don't want this person to feel uncomfortable at work but this is also my home and I believe his fear of dogs has resulted in him misinterpreting the situation.