If they were going for the kill... They would have killed the owner that approached them.
The guns are drawn in case they can't see the felon. For example, a felon sees cop cars approaching and ducks down to not be seen, while he loads his handgun.
Until they have a grasp on the situation, I can see why a person would want to protect themselves with a gun when approaching a suspected car thief.
They're not setting up a sting or a trap or anything; they're going straight for the kill. That's a problem.