Whenever possible, you should report wrongdoing to the police instead of taking action on your own. Police officers are equipped with the proper intervention tools and trained to deal with incidents which may escalate to become violent.
What You Need to Know About Making a Citizens Arrest discusses the processes involved in deciding if you are in a position to make a citizen's arrest. The publications warns that a citizen's arrest is a very serious and potentially dangerous undertaking. Unlike a police officer, private citizens are neither tasked with the duty to preserve and maintain public peace, nor properly trained to apprehend suspected criminals.
Exercise extreme caution when attempting to make a citizen's arrest. It outlines also how to identify when, or if it is appropriate to make a citizens arrest and the due processes that must be followed.