Sounds like the guy had a mental illness that went unchecked and eventually overwhelmed him. It's really a sad story to tell the truth, but I have a hard time even considering that marijuana was even a significant contributing factor.
10 grams a day does sound extreme. I don't even use 10 grams a week. 3 joints first thing in the morning? I usually take maybe 5 or 6 puffs around lunch time or so, just on the weekends. After I've had my coffee, breakfast and have gotten good and woke up. If I do work around the house, it might be 4 or 5 in the evening before I light up. After I get the work done. I think 10 grams a day is for a patient who has a seriously debilitating condition and is not trying to function normally. That's just too much pot. Smoking like that will eventually burn a person out.
But, I do have a friend who smokes like that. She is such a total burnout though. She can't enjoy marijuana like I can because if she's got it, she smokes it constantly like cigarettes. For rec and light medical(I use MJ to help me sleep at night), moderation is key. Actually, in everything you do moderation is key. If you like to eat and eat all the time you will get to 500 pounds and have health issues. I had a friend die last year in his early 40's. He drank every waking hour of every day. And he had been hospitalized prior to that for serious issues, heart, circulation(his face was always dark red and blue colored) and the doctors warned him. He didn't even slow down. Now he is gone.
Anyway, I feel bad for that guy and his family, but, I honestly don't think MJ was significant in his demise. He has other major mental issues that went unchecked. I'm not a doctor or a scientists though.