That tweet was published in the wake of the George Zimmerman verdict. Shortly thereafter, Ms. Silva deleted it. She subsequently either deleted her entire Twitter account or limited access to it.
Ms. Silva is (or once was) a reporter for the Associated Press.
According to Muckrack, which has access to her tweets, she explained that she was simply making a joke about Justin Bieber. Or teenagers. Or something.
Hat tip: Jeryl Bier.