There is no easy way, but telling him calmly, and in the most caring way possible would be my way of doing it. As for the boys reaction? who knows, we all react differently, but stand by for whatever way he reacts, and be a solid support for him.
tell him gently and don't worry how he will act he is going to be destroyed.
Sit him down and explain his mother is gone, she will be watching him forever but he will not see her. He will feel her, she still loves him, and misses him deeply. He may need a professional if he can't cope
Ouch. Had to do that when my son was 11. I did it as straight forward and gently as I could. At first he was just numb as I held him. Slowly he got to feeling better.
You just have to keep on giving all the support you can and when question come, answer them as best you can in the most gentle way you can.
Be truthful and explain that this is one of lifes realities. Make sure you let him ask questions and answer him honestly. Also make sure he knows he has someone to come to when he needs. I had to do this years ago with my 7 year old daughter. Make sure you allow him to grieve in his own way.
Sorry for your loss :((((
I will tell him what happened, and you'll be there. He will be devastated. Be ready to give him lots of hugs.
Show him the scene from Bambi when her mother is shot by the hunters & say " see that? , that's happened to your Mum , not shot just dead" job done.