I wish they would just explain why he killed his parents like did they try and hurt him or...

It was an accumulation of misunderstandings between him and his family. He thought his family was avoiding him because they didn’t love him and he also thought they forcibly had him sent to the war at such a young age because they hated him. So he decided to get his revenge by killing them since he thought they wanted him dead too. But as was seen in the most recent chapter it was all a huge misunderstanding since his family actually loved him a lot.

thanks for explaining :)