Well, I'm sure glad that's not true everywhere. That takes "punishing the whole class for the misbehavior of one" to a twisted extreme.
If someone is murdered in the commission of a petty burglary, the murderer, and accessories should be charged, and not the one who stands there in horror with their mouth open.
No, if you witness a crime, that you weren't expecting to happen, you report it immediately to LE and you are not held responsible for it. If you are participating in a robbery, and your co-hort decides to kill the store clerk, and you just leave with him and keep your mouth shut, then they look at the film in the store and see you there, whoops, now you are hung with it.
Seems totally fair to me.