This article explains that French investigative procedures require a great deal of secrecy, and personal privacy for individuals, so much so that rumours and leaks aren't always denied, thus allowing lots of misinformation and unfounded theories to thrive.
http://www.independent.co.uk/news/w...rench-judicial-process-that-lets-8223361.html
For example, the story about the chief suspect being the former member of the French Foreign legion, seems to have originated with a book published (or perhaps "rushed into print") by the UK tabloid The Mirror. They claim to have been given an "exclusive interview" by the French prosecutor, who allegedly revealed this bombshell about a prime suspect only to them (not to the Fench media), just in time for their book to go on sale. How terribly convenient. It was reported as fact by all the English media.
However, in a french language article I found this statement:
Also, this ex soldier was a one point a paratrooper, but somehow through the magic of headlines (where you can say anything) he became a "sniper". Becoming a sniper is very specialized training, and I don't believe he ever had it, it was just made up because it sounds more compelling.
Also, someone claimed he "wrote a letter" saying he was committing suicide because he couldn't bear to be considered a suspect, but apparently he must have said a lot more than that because his suicide note was 7 pages long. However, no one's going to discuss the other reasons for his suicide listed in the letter.
https://www.gq.com/story/alps-murder-the-perfect-crime
All in all, I would say the media are extremely an unreliable source of information in this case, and anything they report should be taken with a large dose of skepticism.