The note makes mention of the recent mall attack in Kenya and the suicide bombing at a church in Pakistan. The note did not contain any specific threats, but police are investigating.
The Islamic Center is offering a reward for information on who may have left the note.
See also “MURRIETA: Suspicious note discovered at Islamic Center”, Press-Enterprise, 25 September 2013
Update: See “MURRIETA: Man who left suspicious note at Islamic Center identified, police say”, Press-Enterprise, 27 September 2013