What you should do --- back away and watch the tail.

They swing the tail around in a sweeping motion to knock you off your feet and toward their mouth.

How quickly they can do this and how far the tail can reach catches a lot of animals/people by surprise. I've seen them do this to dogs --- and dogs generally have pretty good reflexes --- better than the average people.

Once you're on the ground and less mobile, they attack with their teeth/jaws.