Let them release his martyrdom video, like they do with the others.
He would not have sent anything to ISIS in advance, for fear of compromise by the FBI/NSA etc.
The scene has been more tightly controlled than any I have ever seen. Not even his driver license photo has been released! He could have left Antifa/ISIS literature all over the hotel room, his houses, and on his computer, and we may never know it.
Not unless he mailed out information packets to multiple media outlets. In that case, we might learn the truth. Otherwise, it will always be a mystery.
Let them release his martyrdom video, like they do with the others.