hello Kizzels, I sincerely want to offer my deepest condolences to you, I can't imagine the thought of something like this to happen and then try to cope with your ongoing life, but I'm proud that you have come to this site, where no doubt all of us have a soft spot for you.
There will your days when you feel better than the previous day and unfortunately this will be the case for awhile, but those good days are what you have to try and build on, and there will be no explanation why you have those terrible days, even though you will know why, and we will also know why and that's where we understand how you feel.
Your other son must be feeling the same pressure as you are, but he will probably keep it quiet to himself and won't be able to open up until he is ready, but when he does go to school he will get much support, but perhaps this could be too overwhelming for him all at once, so it maybe a good idea to go and see the principle, but I know that even doing this will be extremely difficult for you.
You are entitled to feel free to open up yourself, there's no shame at all, because you have had some absolutely awful news so please show your emotions.
Try and keep busy as you say, enjoy the antics of what your puppie gets up to, it won't fill the spot left, but what it will do is to take you to another part of your emotions that you do love, just as your other son will also find other some comfort.
Please reply back to us. Geoff.