Bild cited a police spokeswoman who said the man had run through a nearby allotment and began attacking people at random on Friday night.
He stabbed three people at the party, seriously injuring one of them.
Police were then called to the home of the family that was hosting the party on Genossenschaftsweg in Wolmirstedt, near Magdeburg in Saxony-Anhalt around 9.30pm.
The attacker, whose identity has not been made known public, was then shot by the police and later died from the gunshot wounds in hospital, according to Bild newspaper.
The party was organised to mark the start of the UEFA European Football Championship, where host country Germany faced Scotland.
