this incident has a little background, and the officer may have had more probable cause to stop Brown than just jaywalking:
“This QuikTrip is where things started yesterday with this case, based on various accounts,” French said. “Mike and his friend were accused of stealing gum from the store or some sort of cigarettes.”
http://cltv.com/2014/08/11/photos-riots-looting-after-fatal-shooting-of-missouri-teen-by-police/
http://www.freerepublic.com/focus/news/3191792/posts?page=9#9
That has not been confirmed even though it would be simple to do for the police.
Either way there was no police dispatch on the matter that this officer would have received.