He prosecuted Nicola Sacco and Bartolomeo Vanzetti for armed robbery and murder in a case that drew worldwide attention.

[3] From 1896 to 1902 he worked as an assistant superintendent of the Hyde Park, Denham and Milton Light and Power Company.

The two opened a second office in Boston and in 1905 former district attorney Thomas E. Grover joined the firm.

However, he remained involved in later phases the Sacco and Vanzetti case by representing the government as a special assistant to the district attorney.

[4] In addition to his work as an attorney, Katzmann was also the longtime president of the Hyde Park Savings Bank as well as a trustee of the International Trust Company.