Apparently they were found in a "Storage lot auction". That's where a storage lot is unpaid/abandoned and the lot owner sells whatever is in it to the highest bidder. Fortunately, the winner found the rolls of film and didn't just throw them out -- like most people would have. I assume the owner of the storage lot must have records of the owner, but you are right, the photographer is probably dead. S/he was obviously an experienced photographer -- skilled and with good gear -- and politically savvy. Obviously not an 18 year old punk.
I'm sure there will be more clues as the photos are examined. Lots of people in those photos know who was behind the camera, and with enough PR will be uncovered.
Just beautiful work -- I hope a documentary is done when all the rolls are developed.
Does anyone develop Kodachrome today?????