I need help.. suicide and murder please read!!?

Ok so my nephew is 15 and he seems to be a really good kid but doesn't get along with his parents. I never thought it was a serious problem because what teenager doesn't argue with his parents here and there.. So about 3 weeks ago he got caught smoking weed and arrested and his parents were furious and told him that he was going to be sent to Admiral Farragut Academy which is a military school (I think) So he got very violent with his mother when she showed him the brochure to the school however his father came a kicked his a** .. So about 4 days after that he got a hold of his fathers Glock G34 hand gun and shot and killed his mother.. Then he turned the gun on himself.. I am so depressed for my sister who has died and her husband.. I feel that my health is deteriorating quickly and I have began to have more flares of gout and other conditions that I used to have under control with medication.. Do you think it would be good to talk to a counselor or do you think I need to go all the way to a psychiatrist? My sisters funeral is coming up and I know that I need to be there and stay strong for the reset of the family, but i'm not sure if I can do it.. Please help!?!?!