I used Google Book Search to search for the phrases "My dad was a famous two gun man" (note "gun man" is two words or possibly hyphenated) and "As Loose-Trigger Pete" and I found that both phrases can be found in:

The Judge [an American humor magazine]. New York, N.Y.: Judge Publishing Company, v. 82, Jan-June 1922.

WorldCat might help you find it in a library near you.