A jury found the neighbourhood watch volunteer not guilty of murdering Trayvon Martin in Florida last year (Feb13) after Zimmerman claimed he shot the teenager in self-defence, but Saturday's (13Jul13) verdict sparked outrage across America.
Several demonstrations have already taken place, with Solange Knowles leading a peaceful rally in Brooklyn, New York on Sunday (14Jul13), and on Monday evening, hundreds took to the streets of L.A. to protest against the ruling.
However, 13 people were arrested during the protest, in which a news crew was attacked, according to The Hollywood Reporter. The L.A. Times also reports cops became involved in a stand-off with protesters outside a Walmart store.
Hannah called for calm, writing in a post on her Twitter.com page, "Be peaceful out there - streets shut down in Compton. Justice for Trayvon!"
Osbourne added, "I'm all for the Trayvon Martin protests I just wish they were peaceful protests rather than riots don't let the message get lost to violence!"