If you are a free-falling observer, _nothing_ changes for you locally at the event horizon. You will cross it and reach the singularity within a finite (and quite short) time.
If I to guess, you'd see yourself outside an smaller event horizon (as nothing gets through one due to spacetime warping) and you's have a lot of mass very far behind you due again to space time warping so that yout local scape velocity is less than c.
An event horizon forming in front of you doesn't change anything locally. You'll just find out that however much you try, you'll be moving towards the singularity with greater and greater speed.
A point-like particle won't be able to tell that anything is strange until it hits the singularity. But an extended object will break apart due to tidal forces that become infinitely large.
This is for a non-rotating black hole. I can follow the math for it, but rotating black holes are just too math-heavy for me.