In 1953 Seifert's tuberculosis was found to be inactive and he was declared to have a reduced earning capacity of 30%, though any causality between his illness and his imprisonment during the war was denied.

Seifert contested this, accused the doctors of creating false medical reports and complained in long letters to various authorities about his problems.

[citation needed] Meanwhile, Seifert revealed to his brother that he had a plan to kidnap young girls and hold them captive in the cellar of his moped trailer.

On 7 October 1955 Seifert married Renata Urszula[4] and reportedly fell apart when she died of an embolism during premature birth on 11 February 1961.

His flamethrower was made from an insecticide sprayer with a wire netting attached to the nozzle, and filled with a mixture of old motor oil and paint thinner.

[5] On 11 June 1964, shortly after 09:00, Seifert approached the schoolyard of the Catholic elementary school located at Volkhovener Weg 209–211, armed with a self-made flamethrower, a spear and a mace.

Seifert ignored them and, after blocking off the gate with a wooden wedge, proceeded towards a girls' physical education class led by teacher Anna Langohr at the schoolyard.

When teacher Gertrud Bollenrath stepped out on the schoolyard Seifert fatally stabbed her in the chest with his spear and then approached the barrack where Ursula Kuhr and Mrs Kunz were teaching.

Seifert fled the school compound and attempted to kill himself by swallowing E605, a poisonous insecticide, but as the substance was diluted he did not die immediately.