Daniel Gore, 46, died during during brain surgery for an illness, according to local media reports.
His brain condition was discovered in hospital and he died during surgery for that condition, the reports quoted Surrey Royal Canadian Mounted Police spokesman Cpl. Bert Paquet as saying.
The police are now investigating whether it played a role in the crash.
"It's obviously a possibility we have to consider. It certainly brings a challenge, that we never had a chance to ask (Gore) his recollections," Paquet added.
The five deceased were identified as Pawandeep Arjot (31) her two children, Annish Sachdeva (5) and Jessica Sachdeva (3) her sister-in-law Neelam Dhingra (47) and her mother-in-law Vidya Sachdeva (68).
Pawandeep's husband Gurmeet owns an Indian sweet shop in the Surrey district of British Columbia.