news:e2a10518.0307030855.577d9ff3@posting.google.com...

Only a vet can examine the cat to determine if he has been fixed "properly".

Neutering a male cat does not necessarily stop aggressive and spraying
behaviors, but it does usually reduce them.

What you're seeing may be misplaced or redirected aggression.  The
aggressive cat isn't really angry with the other cat, but is actually angry
about something else.  Since they're indoor-only cats, the aggressive cat
may see or smell a rival cat outside and is reacting to that.  Since it
cannot attack the rival cat, it will attack a person or another cat that
happens to be nearby.

Your cat may also be expressing frustration, such as not being allowed to go
outside, not being fed on time, an unwelcome visitor in his territory, etc.
Think about what is different about the days the cat is aggressive from
other days.  This may yield a clue to the cat's behavior.

If the cat that was attacked was taken to the vet on the day it was attacked
or taken outside the home to another location for a while, the attacking cat
may be reacting to the strange smells it detects on the other cat.

Bill