The article author wasn’t saying George Floyd was murdered. It reads “the post–George Floyd murder and car crash sprees”. The word “murder” goes along with “and car crash sprees”, meaning the spree of murders and car crashes which followed the death of George Floyd.
It’s implying that George Floyd was murdered. It’s “George Floyd murder” AND “car crash sprees”. Those are the two items after “post”.
At least, that’s how my English teacher would have instructed me to read it.