Schmitz received his elementary education in Metz, which was part of Germany at the time, and then studied in Munich at the State School of Applied Arts from 1916 to 1920 and the Academy of Fine Arts from 1921 to 1923. He emigrated to America in the last year and studied in New York at the Beaux Arts Institute of Design in 1926-27. Meanwhile, he worked as a modeler in terra-cotta factories and ornamental shops in Perth Amboy, New Jersey. At various times, he was an assistant to Paul Manship, C. Paul Jennewein, and Carl Milles and opened his own studio in 1930.
Schmitz worked on several projects in Washington beginning in the 1930s with sculptures for the Federal Triangle in Washington. In 1933-34 he modeled a number of plaster reliefs for the interior of the Department of Justice Building, Washington, based on designs by Jennewein. On his own, Schmitz executed the full-length statue City Delivery Carrier (1863) for the Postmaster General's reception room in the Department of the Post Office Building in 1935-36. The following year, he carved a limestone overdoor panel, Foreign Trade, for the Federal Trade Commission Building. Later, in 1959, he restored Luigi Persico's sandstone figures of War and Peace which had adorned the east front of the U. S. Capitol since the mid 1840s. (They were subsequently replicated in marble and the originals placed in storage). In 1960, Schmitz designed an overdoor relief panel for the main doors for the Embassy of Iran.
Elsewhere, Schmitz executed four marble reliefs for Loyola Seminary, Shrub Oak, New York; architectural sculpture for the Federal Court and Post Office Building, Covington, Kentucky; seventeen reliefs for the Physics Building at Michigan State College; and four heroic groups for the 1939 New York World's Fair.
He won a number of awards during his career including the National Acadamy's Watrous Medal in 1959 for his terra-cotta relief Joy of Life (cat. no. 4). He was a member of the National Sculpture Society, the Architectural League of New York, the Audubon Artists, and the New York Society of Craftsmen.
