Odds are 20 to 1 he’s Shia.
Germany is supplying a lot of small arms to Sunni rebel in Syria.
Assad is Alewite, which is a Shiite sect. Iran is supporting Assad and has units fighting there.
Possible motive, aside from regular old Muslim blood lust.
There are so many ethnic groups and religions in Iran. It is possible that this shooter is from one of the minorities.