Okay, it is on the front page of the thread, this makes it legit, got it...
By just using your brain, you could decide for yourself:
Let's just assume that AT&T is a mobile carrier in France.
The picture shows the time of the tweet as "5:09 PM" but according to the police, the shooting started at around "5:50 PM".
But no problem: we could take into account summer saving time, wrong time stamps and so on.
The post with the picture itself was made by The Vrist at 10:59PM (CET, but in Germany it's actually 11:59PM) and here is the obvious fact:
The shooter is pictured from two different angles. One from the street level and one from a window...since it woud be totally crazy to assume that the photographer took the photo from his window and
then walked down on street level
and crossed the street to take a close up of the shooter, a normal person simply has to assume that the pictures were taken by two different people.
And it is
absolutely impossible that these two alleged photographers met before 10:59 to mend their pictures for this tweet.
Got it?
So, you're saying this is fishy? Oh, yes, it is!

I know, it must sometimes seem so easy for you to just take anything to get your stupid agenda across but this one here is just a fail.

Or, the person who was in Germany, was french, took the picture on ground zero, then ran for cover in an upper ground ally, or stoop, took another.