It was probably HIAG and now he's going to brag about his wonderful "wum" against Dortmund. Hope whoever's responsible, even if not HIAG, gets caught quickly.
Clubs have enough money, I would suggest they all up security. They are a clear target and with this happening it'll spark that idea in the minds of other terrorists just like the attacks with vehicles inspired others to try it.
Do we know for sure it was a terrorist? Not to be funny, but a terrorist would surely have not made such a piss poor bomb. How do they know it wasn't just some batshit crazy Bayern Munich fan?
Doesn't look like a very sophisticated attack. You're probably right, it was somebody acting alone who designed something they had to hand with some fertiliser and a few household chemicals. Still, it should be a wake up call to Football teams, it could have been a lot worse.
They've nicked a bloke with "Islamist links", but that could just be rounding up the usual suspects. Probably another one of these internet radicals who looked up how to do it online and claims to be part of ISIS. Getting a bit too common, unfortunately.