It basically means he's too unwell to contribute to his trial meaningfully and not fit to enter a plea. He probably won't attend his trial but he can do - Odesa Carey, who killed her mother, did and was shouting from the dock that her mother was still alive.
We'll no doubt get to find out more about why and what his diagnosis is during his trial of the facts. I'm guessing an indefinite hospital order will be the result.
However, it does irritate me when people think that this is somehow "getting away with it" when what our focus actually needs to be on is why these mentally people are in the community free to harm innocent people. Focus on why the system is failing so badly.
I'm not saying we should go back to the old days of just institutionalising everyone, far from it, but, in the last three months alone, I have followed at least five to ten cases where mentally ill people have killed their parents, grandparents, strangers and there have usually been numerous warning signs.
We HAVE to do better.