[@Sep] Just some infantry/security guard-ish dude. He'd be low ranking if possible, since it's always more fun to work your way up where possible. Basically, he carries a rifle and he follows the orders from above (likely to be the head of security, mr. Turov, or an officer of sorts). 

Would that be too low in the ranks for you? I am assuming that for a ship this large, infantry would also mean military police.