Here is my speculation after seeing this
Video
Residents (in Bavarian dialect). "You asshole, you dog, you dumb wanker"
Perpetrators: "because of you I was bullied, for seven years."
Residents: "You're an asshole."
Perpetrators "and now I have to buy a gun to shoot you all down" ... "
Residents: "ah weapons? your skull should be cut off you asshole."
Perpetrators: "shit Turks."
Residents' Kanaks shit. "
Perpetrators: "I am a German."
Residents: "A wanker you are!"
Perpetrator: "I was born in Germany, in a Hartz-4-area"
residents, "You dumb dog you"
Perpetrator: "I was hospitalized."
Residents: "Yes treatment, you belong in the psychiatry asshole, stupid."
Perpetrator: "I have nothing done ... shut up, man."
The translation might be not 100% correct!
Anyway, in the video you can hear that the shooter/perpetrator got also an Bavarian dialect.
I belive him that hes a german. He might have turkish/islam roots or whatever.
But from what he was yelling ther I belive that he was just a sick asshole who shoot serval people down.
I guess in the next few days a lot of people will use the dead bodys for ther respective propaganda :/
(Sorry about my bad english again, hope you understand it)