Agree with the high alert thing.
When I was about 21 I lived in a particularly ropey tower block.
I got in the lift once to go to my flat on the fifth floor and just as the doors were about to close a bloke go it.
He looked to be in his fifties, he was built like a brick shithouse and he had blood running down his face.
I took one look at him and legged it out of the lift.
He called back at me that there was nothing wrong with him etc etc.
I actually think he had a medical condition causing his face to bleed and he had seemed harmless enough when I'd seen him around.
However, I had no control over my reaction. The lift doors were about to slam shut with just the two of us inside and I was terrified on a visceral level. I couldn't reason it away, I couldn't think logical thoughts about why his face might be bleeding.
I just legged it.
And he was offended and 'called me out' for it instead of beginning to understand how I might have felt.