Some companies have policies in their manuals covering this kind of situation. Because you asked this question, I am assuming that you do not have such policies in place. I am also assuming that you want to terminate this individual’s employment instead of waiting to see the outcome of his arrest.

I do not know if you are located in an "employment at-will" state. But if you are, you can terminate this employee at any time. This would also assume that you have no employment contract with the employee and/or a written policy stating to the contrary.