Karl Siimann was born on 26 March 1928 (place of birth unknown) and lived with his parents in Tapa, an important railway junction in northern Estonia. Siimann was a common name among the Roma who had arrived in Estonia from Latvia during the second half of the nineteenth century. 159-member strong, the Siimanns were the third largest extended Romani family in Estonia. About three out of four family members did not survive the German occupation of 1941–44.
On 1 June 1942, the police arrested Karl Siimann and placed him in Paide prison. Pressed by a police interrogator to reveal his job and housing situation, Siimann stated that he neither stole nor begged. He had recently worked at Tapa railway station chopping and loading firewood. Getting a job as a young person was simply impossible, he explained. He received a weekly wage and free food. Karl Siimann was illiterate and therefore asked Richard Siimann (unknown–unknown) to sign the interrogation minutes on his behalf. Assuming that Richard was his father, both individuals—as well as Karl’s grandmother, Leontine (unknown–unknown)—lost their lives alongside 240 other Roma on 27 October 1942. Prior to killings, the Roma were incarcerated at Harku prison, southwest of Tallinn.