Aachen public prosecutor Robert Deller said on Thursday that the man turned his gun on himself before the police could arrest him.
The 63-year-old man from the town of Langerwehe in North Rhine-Westphalia shot dead his 64-year-old wife with a small-calibre rifle on Wednesday night, before turning on his neighbours.
Police said he then woke up his neighbours by ringing their doorbells and knocking on their doors every quarter of an hour - shooting those who answered.
A 52-year-old woman was caught by a bullet in the neck, while a 61-year-old man at another address was hit in the shoulder. Another man was shot through the neck and jaw.
Their lives are not thought to be in danger but the gunman is said to be in a critical condition after shooting himself.
"We have not been able to make any connection between the victims that would explain these acts," said Deller. He said the neighbours were lucky to survive.
Police have launched a murder investigation.