I'm not sure why he/she would do that, but I think it might be pretty normal. Even cat's that are tame will get kinda wild when they are out and about.
I'm sure Tinky is spade, but if not maybe that set him off...............

Too bad you can't catch him and then you could have 3 cats! He-he-he.

You could probably get a trap from an animal rescue place- I think they will loan them out to people.