My understanding of the pursuers' account of things is that they were along side him for a while before the video starts, asking/telling him to stop and that they wanted to talk to him, maybe they indicated police were on the way also, or maybe he could have easily heard the father in the bed of the truck on the phone with police (I believe he was on his cell in the truck)
If this is correct, then they were in a position to see how he was behaving and reacting up close, and based on his behavior and reactions, combined with having seen him exit the property he was trespassing on, and apparently having seen him on other videos previously or seen him around at the time of other crimes, it may have been 100% obvious to them that he was fleeing / not jogging while oblivious to them.
I think their every action speaks to them having certainty based on their much better vantage point than we have, that this was a criminal fleeing the scene of a crime who didn't want to be held up until police could arrive.
His launching an assault on them when they got out of the truck only serves to confirm that that was what he was.
The idea that he was just blissfully ignorant, jogging along, hadn't even noticed these guys or this truck, only to finally notice them when they were in front of him with guns, is a silly and implausible narrative in the extreme.