It ignored other humans, Filch was standing close enough to be spattered with his cat's remains, there is no way he could have outrun the troll. He was alone and it's stated that trolls go for isolated targets, the only reason the troll would have let him go is if it was commanded to.

I do retract my later claim that Lucius wouldn't care about other Hogwarts students, it should have occurred to me he wouldn't risk his allies' children.