Jack Rockwell
Jack Rockwell Trowbridge was an American film actor who was born in Mexico. He appeared in over 250 movies, mostly Westerns, between 1927 and 1947.
Rockwell's older brother was character actor Charles Trowbridge. In the 1920s, prior to embarking on a professional career as actor, he worked as a fireman.
His death in 1947 was due to hypostatic pneumonia, not a "nervous breakdown" as claimed on IMDb.