Not enough information to yet to make a reasonable response.
Did they know each other?
Had they been involved?
Is there proof that she was a burglar and not invited in?
Was the force reasonable,?
What was his competence level in the force applied?
Was he a LEO?
What is the standard procedure in the jurisdiction?
Is this a check the box reaction by the PD in a lethal situation?
Is he being charged or just taken in for questioning?

What are the castle laws there?

From the title alone no. If you break into someones home you are putting your life at risk. The homeowner has every right to defend himself his home and his family. I didn't click the link, but hopefully this happened in a state where it's legal to defend yourself with lethal force.