Oh I am so, so sorry.
I know exactly how you feel - I have blamed myself for every chicken that has died in my watch.
But please don’t.
As others have said accidents happen. With time the guilt and grief will subside (though probably will never go entirely) and you can remember him for all the good times.
Don’t do anything hasty. That you care so much tells me you are absolutely NOT horrible at this.
Maybe the best way to honor his life is with all the other chickens you will care for in the future.
Think of a memorial for him - maybe name the coop after him, or plant a bush.
And in the meantime,