You said"This is not an example of someone defending their property " what was it then, did that stolen property not belong to walmart?
That part of this situation was already over. Wal-Mart's employees had already aprehended and subdued this man. If that is as far as it had gotten, I would say "good job."
But that's not where it ended. After capturing this man and protecting Wal-Mart's property, these guards proceeded to apply force that ended up killing this man. They killed him after they had succesfully done their jobs.
That's the difference.