You appear to be of the opinion that humans CAN do something about a ‘killer’ space rock.
Care to elaborate?
Pop it with a nuke while it’s still a month away. Or in a prior swing by, as it is headed away. We certainly can get one there.
That will either:
Give the asteroid a slight nudge. (It’s probably a nickel-iron solid body if it holds together.) With the scale of space involved, “slight” means it will miss Earth by millions of miles.
Break up the asteroid. (More likely, as many are essentially closer to gravel piles than solid “rocks”.) The force will still put the pieces on new trajectories, slightly different than the old trajectory. Once again, with the scale of space involved, “slight” means they will miss by millions of miles.