Maybe because they,the police, weren't knowledgeable with the workings of a .22 semi-automatic rifle.
The fact that there were two shots and not just the one ? No-one can shoot themselves twice.
Had the second shot replaced the first one then there'd have been no case to answer.
Really and truthfully,I should be mystified by the first shot and not the second,although I've said that the first shot was a " mistake " and I haven't always believed it to have been self-inflcted as it isn't even a contact one which you'd expect if/when someone takes their own life.