It sounds like a the operator of the scooter slowed unexpectedly while being too far out in the lane, or, the dump truck driver misjudged and had to brake too hard to avoid hitting the scooter, which caused the truck to veer, but, it's the veering that seems to be an issue, since the truck should have continued forward without veering that hard, so, perhaps the truck was not maintained properly, which is a common issue with many dump trucks...

And, hopefully, the driver was not distracted by talking on his cell phone - just this morning I took a rare phone call while driving, and, it is very distracting, even with a headset or blue tooth device...

My sympathy to all involved in this accident - I was involved in a fatal car accident many years ago, and, certainly know what emotions are involved here...