My condolences on your loss.
If your son was a Canadian citizen, could the Canadian Embassy be of help to you? I would think the Embassy must be notified of a death of a Canadian citizen abroad, and has procedures for dealing with such an event. They may also have recommendations for local physicians in Bangalore who could be of help.
The postmortem examination and related test results may take a while to be completed. Until then, it may be hard to determine the cause of death, and sometimes it remains unexplained.
Again, I am sorry for your loss.