Did she know they were the cats owners? Had she tried to contact them in the past? Were they ignoring the issue? I don’t know, do you?
I’m not saying that there wasn’t a better way for her to handle the problem. But, I believe she was well within her property rights to take care of the issue as she did. Is she a jerk? Maybe. Or maybe she was just fed up with the problems that a stray cat visiting your property can cause.
Why ask all those questions? This isn’t about her knowing the owners, or an “issue”.
She has already been fired, let’s just hope for some criminal charges.