If you get murdered in Michigan, they won't do anything about it unless someone files a complaint? That seems to be the logical extension of his statement.
Assuming MI criminal law is similar to most states, a misdemeanor has to be observed by an officer, or the victim has to make a citizen’s arrest. Filing a formal complaint accomplishes the latter. An arrest can’t be made on the basis of the video because there’s no way the police can know that it hasn’t been staged or tampered with. At trial, though, anybody who took a video can appear as a witness and show it.