The man suspected of killing his family and himself left a note indicating that he was afraid of being arrested after obtaining the fake certificate, investigators say.
German investigators have said a suspected murder-suicide near Berlin was linked to a fake COVID-19 certificate.
The bodies of five people -- including three children aged 4, 8, and 10 -- were found with gunshot wounds at their home in Koenigs Wusterhausen on Saturday.
Authorities believe the 40-year-old man had shot dead his wife and children before killing himself.
Prosecutor Gernot Bantleon told the German DPA news agency that the man had left a note saying he had procured a fake vaccination certificate for his wife.
COVID-19 certificates were made mandatory for German employees last month as the country tightened its anti-virus restrictions.
His wife's employer had reportedly found out and the couple was afraid that they might be arrested and their children taken away, Bantleon said.
Police were alerted after witnesses reported seeing dead bodies inside the house in the Senzig district of the town, southeast of Berlin.
Investigators said they had found a gun in the house, but it wasn’t immediately clear whether it was the weapon used to fire the fatal shots.
They found no indication that anyone else was present at the time or that anyone forced their way into the house.