Ever spoken to a person who could be a serial killer?

As a teen I’d go on chat rooms. I spoke a few times to a person who said the most horrible things that I never forgot about him. I confronted him one day and he appeared to have changed personality and didn’t know what I was referring to. I still remember his username. It was for teens aged 13-15 then there was another room for 15-19. The place was full of paedophiles.