A car or small truck came around the corner, hopped the curb, knocked over a speed limit sign and smacked into a tree. The tree held, the car's windshield shattered and sprayed glass.
That's the what. The "why" is pure speculation: Somebody drunk, maybe having some kind of medical problem, made the turn going too fast. Hit the curb hard enough to chip the concrete, so we are talking some kind of impact away from the rubber. I didn't see any skid marks on the road, but there were on the sidewalk and lawn, so they hit the brakes.
Maybe they were running from somebody. Maybe they were trying to kill themselves and did it on purpose. Can't tell any of that from the signs left behind. If I had to guess, I'd say it was a young man or woman who had been out to a Hallowe'en party, had too many, and lost control.
Be fun to see if the local news has coverage of it, to see how close I might be in my guess ...