Yes they did know from the 911 call and yes it was the resisting getting in the cop car which led to this event. But it was the passing of fake money which led to the rest of the event occurring. There is always a process or background in these events which we don't know right now regarding a bunch a stuff. But again elements of the media run with their own narrative.
If we take note of the preliminary cause of death we see from this source...[www.washingtonexaminer.com] Floyd did not die from strangulation which is the cutting off of the blood supply which is what compression of carotid artery accomplishes.
Quote from source..."In the charges brought against former Minneapolis police officer Derek Chauvin on Friday, a new finding shows the county medical examiner concluded the death of George Floyd was not a result of asphyxia or strangulation."
So what killed Floyd? Well we have this..."Floyd's underlying health conditions included coronary artery disease and hypertensive heart disease. The report says the underlying health conditions, combined with Chauvin's restraint and any possible intoxicants in Floyd's system, likely contributed to his death."
We will have to know the extent of Floyd's underlying conditions before it can be ascertained if Chauvin's restraint caused or contributed to Floyd's death? Its possible his continued efforts to resist could have been the main cause since he was complaining about shortness of breath when standing up? Shortness of breath or difficulty breathing is a symptom of BOTH diseases. Again the autopsy info shows his death wasn't due to strangulation which is what a knee to the carotid artery would have contributed.
But regardless of the facts about the manner or degree of restraint we still have Floyd's actions and resistance being the major reason why this all takes place.
Now again I'm not advocating for or against in this action just looking at what we know and more important don't know.