colloquialism?

the context is one french policeman working with the resistance, talking about his colleagues who hurt and kill the resistance "patriotes";

i don't know to which of them, the police or the patriots he's referring to when the maquis policeman says:

"Ceux -la, bon sang..."

if bon sang is straightforward, it means of course, good blood, and so refers to the good guys;

but if he referring to the bad french police, then it could refer to their blood needing to flow, or something like that?

tia

isabelle