Seems quite obvious that a pardon isn’t what’s needed. All of their court martial sentences should be overturned and their records, if they still exist, should be corrected to state what happened.
A very disgraceful incident overall reflecting the horrible conditions present in the locality at the time. I had never heard of it, naturally, as it is not something one might expect to hear of in a HS history class. People involved and their families will never get over it.