Custom enemy.

[Statyk]

He's not attacking because you have no animations set in the model's folder. He also needs bones and joints to match the grunts, which you would have to do in Maya or Blender (I recommend Maya)... So I'm guessing the reason he gets stuck is because he is supposed to do an attack animation, but since there IS NONE, he just freezes up.

Your first step is to get Maya and try to rig him up with joints and bones.