The second monster which appeared was the backwards sprinter.
As the name sais.. it sprints towards you with its back turned. Long arms and legs, a rather grey and dark shiny skin and a really ugly face.
It sprints after its prey and when it comes close to the kill, the back of the monster splits into two pieces with wide and sharp teeth while it runs.
Many lost their lives to it. It rather lives in the dark and likes hospitals and long dark floors. Somehow you cant hear when it sprints but feel the teeth when it bites off half of your body while running.
The last time i saw one was yesterday near the sewers of our base. That cunt was waiting for blood and flesh to be dropped down.. We throw away infected animals and these things eat them.
Whatever you do, never try to encounter one, it runs faster than you and it can eat a lot of bullets.
I would personally say that this being is rather blind and uses sound for detection .. that would explain why you dont hear when it runs..
We caught few of them to see how they behave and how their structure is built. Interestingly, it seems like an abnormal mutation to cancer cells while a virus becomes conscious to the instincts of the beasts and acts as such.. just eating everything..