Haven't loved Season 5 yet but I will definitely give it the 2nd half to redeem itself.
I wonder if the hospital cops will realize that Rick killed the 3rd one and then come after the group.
I don't think so. First, they know what Rick's group is capable of. Second, they know Rick's group was ready to go to war over what happened to Beth, whereas they weren't willing to go to war over Dawn. Plus, the other two officers were willing to let Bob's death go just to survive - those two officers probably take that secret to their grave - and if they don't, Rick's group is long gone by then.
I honestly think this story arc is dead.