With this information if they were in the RCAF or any other branch of the Canadian Services and they have been dead for more than 20 year you can request their complete military file from the Canadian National Archives in Ottawa, Ontario. You do not have to be a blood relative to get the file. You can print a copy of the form from their website at Request for file Under "Type of Information Required" check Other and write that you would like their complete military file. The National Archives will write back to you in about 1-3 months saying they have found the file and the total cost to photo copy it. You reply to them and either send a money order or credit card number and you will receive the file in about another 1-3 months.
If the person you are looking for served in the RAF you will have to request their file from the Public Records Office in London, England. The PRO will only release files to next of kin. They will not release the file unless you are a blood relative.
You can usually get more information on the person shot down by looking up the date they were lost in the excellent reference books Royal Air Force BOMBER COMMAND LOSSES of the Second World War by W.R. Chorley. If you don't have access to these books you maybe able to enquire at 12 O'Clock High Forum
If the person's bomber was shot down by a German Night Fighter pilot you maybe able to find out which one by enquiring at the NJG Forum
I will add information as time permits. If you have any questions E-mail Me