Mark was a big flirt, and even voted 'Most Flirtatious' by his peers.

DJ was one of the thousands of mutants that lost their powers after the House of M incident.

DJ was killed in an attack by William Stryker and his men. After he was on a bus that exploded, X-23 tried to rescue him. The last words he said were that she was pretty. Elixir tried to save him, but it was too late.

Powers

Mark has the unique ability to manipulate different kinds of energy based on what kind of music he’s listening to. The specifics of how his mutation works lies within his body. Naturally, there are thousands of vibrations running coursing through him due to his X-gene, but he can access none of them because they’re moving so fast he cannot isolate them on his own. In order to help isolate these vibrations within him, he turns to music that has distinct and precise beats and rhythms to help him isolate a type of vibration naturally residing within him. Different types of music achieve different effects.

For instance, the violent and powerful rock rhythms allow him to emit damaging blasts. Soft, uplifting gospel music allows him to take flight. Strong and solid classical music enables him to erect [presumably telekinetic] force fields. And lastly, the wild and vibrant beats of techno grant him the ability to wield bright, blinding lights.

Mark has a lot of potential with his ability, and a lot of room to grow. To begin, he can learn to master each ability, learning to harness each one to its fullest potential. For instance, he could learn how to focus his light based powers to become invisible by reflecting light, or even hone it into a powerful laser. Eventually, he could learn to fully control his energy blast, controlling them mentally, commanding their each and every move with a simple thought.

Once he has fully mastered the use and application of his mutation, he would be able to access every power currently in his repertoire without any kind of musical aid. If fully mastered, Mark would have learned how to single out certain vibrations in his body mentally, and perhaps even combine the abilities he has now to create new ones.