Any mass that has any considerable fraction of light speed and collides with something else, is obliterated. There is nothing left but a shower of subatomic particles and lots of high-energy photons scattering, racing away in all directions. Just a detail: something with mass will never be 'at' light speed. Always slightly under.
The energy released would be openly distributed among the 2 objects, but each individual object will collide with the same amount of energy as such in light speed and thus, both objects will receive the specified amount of energy and reverse in direction.