Wow, I am so sorry to hear that. I have experienced that kind of tragedy
I had a similar experience happen to me, with someone who mentored me when I was still married. I moved on from the organization that we both worked, but she was hilarious, a great friend, and gave me a lot of great professional advice. But she was a heavy smoker. When I moved away and was getting a new job, I called her up to say hello, since we hadn't talked in a bit and ask her if I could use her for a reference. Her number at her job was disconnected, when I was transferred to the receptionist and asked for her, they told me she had died from lung cancer. I still remember holding the phone and shock for about a minute. When I hung up, I just sobbed for about an hour, it was that sad to me... Remember your friend in the spirit he gave to your existence. In that way, they are truly never gone.