There is no investigation to speak of. The same records that were used at the time to demonstrate that these incidents were lawful killings are now being used against individual soldiers. All that has happened is the passage of time and a reimagining of the past to cast such killings as unlawful, thus allowing the records and testimony of the soldiers involved to be used against them.
These deaths haven't suddenly come to light and neither have the names of the servicemen involved. About the only mystery remaining is the actions of the opposing terrorists, but I doubt any detailed records will be provided by them.
If there is any blame (and it is a very big if) the responsibility lies with the State. These servicemen did not choose to arm themselves or deploy in such difficult circumstances. They just happened to be the ones at that scene, on that day, in those circumstances, making the most difficult of decisions.
They served their country well and they deserve our unflinching support now and forever.