The officer in question was overheard making a comment about shooting Mrs. Obama. The Washington Post reported he used his phone to show a picture of the gun he would use. The comment was overheard by another officer and reported to a superior.
It is not clear how seriously the comments were meant to be taken, but the officer could be referred for criminal prosecution if investigators believe his comment constituted an actual threat against the first lady.
The officer is a 17-year department veteran who worked in a motorcycle unit that is sometimes assigned to the first lady. The officer has been placed on administrative duty.
The Associated Press contributed to this report.