Mo. Rev. Stat. § 542.030: Warrant may issue, when.

Whenever complaint shall be made in writing, and upon oath, to any such associate circuit judge, that any person has threatened or is about to commit any offense against the person or property of another, specifying the offense and person complained against, it shall be the duty of the associate circuit judge to issue a warrant, under his hand, reciting the complaint, and commanding the officer to whom it is directed forthwith to apprehend the person so complained of, and bring him before such associate circuit judge.