Replying...
Intro. 1 company was trying to cure cancer and the other was trying to create super solder for the military. The company trying to cure cancer unintentionally created superheros. The company that was trying to create super soldiers created zombies that began to mutate over time. Over the span of 20 years the zombies mutated several times created more variants of mutated zombies than regular zombies. Varying in intelect, size, strength, super powers in some of the mutated zombies, etc...; the people that signed up for the experimental cure for cancer was cured and gained super powers also. Several people wake up at once including the player with randomized super powers (player gets to choose their own) after the automatic cryofreeze system released them simultaneously. They were placed in cryofreeze in a hurry due to the city falling into a panic after everyone got their injections due to zombie attacks. Then after everyone woke up they have to learn to survive in a zombie infested world.

The apocalypse

@Joe