The Warren Commission files that were not published in the 1960s are the primary documents.
Many have been released in the past few years.
The witness testimony of several witnesses is the primary documents.
They are all included in the book.
Read it.
I’m not reading DiEugenio’s book. Honestly, I’ve only read a few of them. Not how I want to spend my time. But I’m familiar with DiEugenio. I’ve had contact with him. DiEugenio has even cited me, over something he and I happen to agree about. But DiEugenio is a well known conspiracy nut. If he gets something right it’s just a lucky coincidence.
If you want to tell me what primary sources he’s using for this claim, I’ll look at them.