So he's previously fired upon a car.
He was in possession of an illegal weapon.
He then shot a burglar with said weapon.
He refuses to acknowledge that he was wrong to do so.

And you're wondering why he's in prison?

1) In the UK is is not legal to shoot a burglar. You can debate whether it should be until the cows come home, but the law remains.
2) He doesn't appear to have any regard for UK firearm laws. 3 firearm offences that I can see.
3) He doesn't appear to understand that he is in the wrong.

And you think he should be on the streets?