“.I do hope Amazon can be held accountable!”
If Amazon had reports on the driver being violent in the past, then, yes. But if they followed all the relevant laws and regulations and conducted whatever legal due diligence is required, no. Note that some states are making it illegal to do background checks. Also, some venues are making it illegal to not hire because of prison records, etc.
Under agency law Employers or contracting agencies are responsible for the torts committed by their agents while performing duties.
In this case delivering packages is 100% acting as an agent of Amazon. The uniform just cements it.
A good Philadelphia lawyer would be inclined to have a different opinion! My guess is that if this woman is smart, she will accept the services of an excellent ambulance chaser. If she hires such a person, I'm guessing that Amazon will settle out of court with the stipulation that the settlement be kept confidential. If she plays her cards right, she will become a very wealthy woman.