What exactly happens when a (hypothetical) antimatter black hole merges with a 'normal' black hole?

Let’s look at two cases

1) Both black holes have the same mass
2) The ‘normal’ black hole is slightly heavier

What happens when the antimatter black hole disappears beyond the event horizon? Is there an explosion, but all the photons remain trapped? If not, is the new black hole simply twice the size?

For case number 2, can the additional normal matter somehow reappear, e.g. as a result of the enormous explosion?