Section 629.37 - WHEN PRIVATE PERSON MAY MAKE ARREST
A private person may arrest another:
(1) for a public offense committed or attempted in the arresting person's presence;(2) when the person arrested has committed a felony, although not in the arresting person's presence; or(3) when a felony has in fact been committed, and the arresting person has reasonable cause for believing the person arrested to have committed it.