As a member of the SS-Totenkopfverbände, while assigned to the Neuengamme concentration camp, he was given the task of murdering a group of children who had suffered a tuberculosis medical experiment conducted by Kurt Heissmeyer.

His first assignment was at Sachsenburg, and his next was Buchenwald, where he participated in the shooting of 21 Jewish inmates on November 9, 1939, following the failed assassination attempt on Adolf Hitler in Munich.

Strippel then served in Majdanek near Lublin Poland, Ravensbrück, then at Peenemünde on the Usedom peninsula, in the Karlshagen II forced labor camp, the site of V-2 rocket production and launches.

In 1949 a West German court found Strippel guilty of 21 counts of murder, inflicting grievous bodily harm, and violating his duty to provide proper care.

In 1965 Strippel, who was still in prison, was investigated for supervising the hangings of 20 Jewish children at the Bullenhuser Damm to conceal the fact that they had been used as human test subjects.

However, the investigation was halted after the prosecutor concluded that he could not prove Strippel had acted with "base motives", which is required under German law for a murder conviction.

Strippel used the money he'd received from the West German government to purchase a condominium on Talstrasse in Frankfurt Kalbach, which he occupied until he died in 1994.