(1) If the accused is in custody upon an arrest without a warrant, a magistrate, upon finding reasonable cause as provided in section 1a of this chapter, shall do either of the following:

    (a) Issue a warrant as provided in section 1b of this chapter.

    (b) Endorse upon the complaint a finding of reasonable cause and a direction to take the accused before a magistrate of the judicial district in which the offense is charged to have been committed.

    (2) As endorsed pursuant to subsection (1)(b), the complaint shall constitute both a complaint and warrant.