Karl Schwartz was a mineworker and a member of the works council at the Zeche Hermann mine in Selm, a member of the SPD (German Social Democratic Party) and a co-founder of the Local USPD Group in Hombruch. From 1921, he engaged in activities as a member of the KPD (German Communist Party) and other Communist organizations.

In 1932, Karl Schwartz was twice sentenced to terms in prison for the distribution of leaflets.
He was held in “preventive detention” from 30 August to 4 October 1933, and was arrested yet again more on 11 February 1934.
Because of his political activities, he was sentenced on 24 January 1935 by the Higher Regional Court in Hamm (“Oberlandesgericht Hamm”) to a term of imprisonment of one year and four months. At the end of his time, he was transferred instead to a concentration camp, presumably Sachsenhausen, and released shortly before the end of the year 1936.

From February 1937, Karl Schwartz was employed as a faceworker at Fürst Hardenberg mine.

On 13 February 1945, he was arrested by the Gestapo. Karl Schwartz was murdered in the course of one of the rounds of shootings that took place in Romberg Park between Good Friday, 30 March, and the week after Easter 1945.