There isn't any actual factual information available yet about the shooter. The shot, yes - accurate from alleged distance of 200 yards indicating a trained and experienced sniper - but no facts on the shooter who escaped so far unseen. I expect CCTV/video from the area is being examined by law enforcement because the murder happened in a public venue.
Trump and his minions stating it was someone from 'the left' does not count as factual evidence.