A 19-year-old football fan was knifed to death at a public screening of Germany's World Cup victory on Sunday night.
A deadly scuffle broke out in a cinema in the western city of Bremen when a fault caused the live broadcast to switch off just as the nail-biting game went into extra-time.
Heavy rain may have been responsible for the sudden power cut at the crucial moment, police said.
Fans moved to another room to continue watching but with tensions running high, a fight broke out along the way – with at least one knife being pulled.
One unnamed 19-year-old victim sustained such serious stab wounds that he died in hospital on Monday morning.
Police have arrested a 22-year-old suspect, who was also injured in the fight along with the victim's 23-year-old brother.
Further witnesses are being questioned in connection with the incident.
Beat and run
Meanwhile, police in southern Germany are searching for a young man in connection with another fatal attack.
Around 3am an unknown attacker struck twice in quick succession in the mountain spa resort town of Bad Reichenhall in Upper Bavaria, police said in a statement.
A 72-year-old man died of his injuries on the street when he was badly beaten around the head, Munich's Abendzeitung reported.
And 15 minutes later, a teenage girl, 17, was taken to hospital after she called police to say she had been attacked a few streets away, police said.
In Berlin, a man fell to his death during a celebratory exploration of the city's rooftops in the southern district of Neukölln.
The 23-year-old had climbed onto the roof of a Neukölln shopping centre together with a friend and decided to hop between buildings.
In the dark, he stepped on a sheet of glass which gave way under his weight and he fell 18 metres, said Bild.
Emergency services were not immediately able to find the man, who died of his injuries at the scene.
Celebrations get out of control
The night ended badly for two fans in Espelkamp, North Rhine-Westphalia, who set their own house on fire with celebratory fireworks.
Willi Isaak, 59, and his wife Irene 52, had been watching the final in their living room, said Bild newspaper.
After the final whistle Willi Isaak let off some rockets in their garden, but didn't notice when one landed on the roof, setting it alight.
Willi then jumped on his bike and headed off to the town celebrations, leaving his wife to continue watching television.
The fire was only discovered after it was too late, after which at least €300,000 of damage had already been caused.
Shot in a motorcade
In Bergheim, near the western city of Cologne, a 23-year-old woman was shot while driving with friends in a motorcade after Sunday's match.
She was taken to hospital with serious injuries.
Police said the other passengers had heard a loud noise and then realised their driver had been wounded in the shoulder.
Police believe she was shot with a small-calibre weapon from outside the car.
An outdoor screening of the game was interrupted in Koblenz, Rhineland-Palatinate, when police received an anonymous phone call warning of a bomb threat.
Police searched the area with dogs and it was later declared safe.
Around 7,700 fans later gathered in Koblenz’s three ‘public viewing’ areas without trouble, police said.
Aggro in Argentina
Outside Germany, violence also broke out overnight in the Argentinian capital Buenos Aires as disappointed fans took to the streets.
In one incident, German tourists watching the game in the same bar as the German ambassador were attacked by Argentinian fans.
Police said two attackers had been arrested.
Overall, 70 people were injured and 50 arrests were made as police used tear gas and rubber bullets to break up the unrest in Buenos Aires on Monday morning.