Police said that Daniel Gore, a 46-year-old father of two grown children, died Sunday afternoon after undergoing surgery for a previously undetected brain tumour.
"We're working with the doctors and medical reports in order to establish whether or not the pre-existing brain condition was a contributing factor to this tragic accident or not," said Cpl. Bert Paquet with the Surrey RCMP.
Investigators say it appears that Gore — who had been the sole survivor of the crash — sped through a red light in his minivan, shearing a car in half.
Rina Sachdeva, 31, Neelam Dhingra, 47, Vidya Sachdeva, 68, and two children — Annish Sachdeva, 5, and Jessica Sachdeva, 3 — were in a Toyota Corolla that police described as "unrecognizable" after the impact.
Richard Fowler, a lawyer representing Gore's son and daughter, says the only explanation for the crash appears to be medical.
"What they know about their father is that he was a very responsible man, a very compassionate family-orientated [man who] coached hockey for Surrey minor hockey, and he was a very cautious, careful driver who just had breakfast with his son that morning, and was driving to work with plenty of time to spare," he said.
Friends paid tribute to Gore on a Facebook memorial page.
"Dan you were an honest friend, a good man, I will always remember the smile on your face and in your heart. You will forever be missed," wrote one friend.
Fowler says Gore's family extends its condolences to the other family affected by the crash.
The Sachdeva family business, a sweet shop, has re-opened after being closed for several days after the crash.
The RCMP says their investigation into the crash could take months to complete.