According to the matter-energy model, matter can be destroyed if enough energy is applied. Atomic smashers destroy atoms and sub-atomic particles. The atom is smashed releasing a vast amount of energy, this energy is in the form of electromagnetic radiation and sub particles (muons, pions, etc.) These particles only survive for a few nanoseconds, until they themselves decay into more electromagnetic radiation, mostly gamma rays and light.
Electromagnetic radiation is not matter.

A black hole is a object so massive that light cannot escape. In the matter-energy model, the matter inside a black hole is squeezed to a point where the atoms cannot take that kind of pressure and they are destroyed. The energy that is released into the black hole, triggers a chain reaction that eventually leads to the black holes death. When the matter is destroyed it doesn’t cease to exist, it destabilizes back into it’s most basic form. It takes it’s place back in the base element, the building block of the universe. Nearly all of the matter in the black hole destabilizes and transforms back into the base element, until the mass of the black hole is all but almost gone.
The energy that was contained for billions of years has now the opportunity to escape, the black hole doesn’t have
enough gravity to contain all the energy. The energy is released in a massive explosion.

Most of the explosion will be in the form of gamma rays, because most of the matter has been destroyed. This can only happen to certain heavy black holes, which have a certain mass. Maybe a galaxies worth of mass. To understand how these black holes get so heavy we must go back to the beginning of all matter.
In the beginning of the universe there was a huge amount of free matter floating around, mostly hydrogen which is the most simplest atom we find in nature. Stars must have formed first, these stars where huge bigger than we have to day. 60 times bigger than the sun. These stars must have formed protogalaxies. After a billion years the cores of the stars collapsed under the stars own weight and formed a black holes. The black hole had a all you can eat buffet at it’s finger tips. The matter was easy to eat and it didn’t resist since it was in the form of gas. A huge accretion disk formed around the black hole, the black hole got heavier and heavier with time.
The black hole grew fast and this lead to it’s own demise.

If we scan the sky I believe we will detect these explosions in the form of gamma rays and light. These explosions would be at the edge of the universe. Since these explosions happened close to the beginning of the universe they are very far away.
And if such a explosion is detected we would have to conclude that the only way such a massive explosion could happen is because the matter contained inside a black hole was released.

There are three things to look for when looking for such a explosion,
(1) The speed of the explosion would be the speed of light. (2) The energy released would be also enormous.
(3) Since matter is being destroyed, we should expect to see a huge amount of electromagnetic radiation and a small amount of residual matter.