Now with all the HIPA Laws it is more difficult than ever to get "private" information, if he was still a minor you may be able to get his records from the hospital, which should have a copy of the run report ( the record of what happened in the ambulance) that should have the names of the crew. If you get that info just be aware that it will contain more info than just the crews name, be prepared for what may seem to you to be graphic info. The info contained in a run report is meant for other medical professionals and might be disturbing to someone who is not used to it.
If Billy was over 18 you will have a harder time getting info, try asking at the ambulance squad or fire dept if the ambulance is part of the fire department.
Unfortunately with all the legalities you may not be able to get that info.
Good Luck with your search.