sentry insurance viking insurance denies liability after authorizing repairs, then changes agents Scottsdale, Arizona

So, 2 weeks ago, while my car was parked in my parking spot at work, an individual decided to cut through our parking lot to avoid waiting to make a right turn at an intersection.  He clipped the back end of my car with the front of his.  Amazingly enough, he was nice enough to come in and tell me he did, and we exchanged insurance information.

I called my insurance company first out of good faith, and they gathered all of the info and contacted his insurance company for me, (Viking/Sentry.)

I was then contacted by one of their representatives, a Ms. Baker, and was told that they would have an adjuster come out to get an estimate on the damage.

Their guy came out, 4 days later, and did his estimate, then asked if i had a repair shop in mind, which i did, and he contacted them to come pick it up for me.

Later that day, I get a call from the shop saying that his estimate is about 50% too low and that they need to have him come to their shop to go over the actual cost of the job and get his approval, which would delay the repair.  I'm fine w/ that.

The guy comes out the next day, and gives his approval to the new estimate and the shop begins work.

Yesterday, I get a call telling me my car is ready to be picked up, but they are just waiting to hear back from Ms. Baker to make sure that Viking/Sentry are sending the payment over. 

They never hear back from her.  So they call the main office number and find out that my claim has been transferred to a new agent, who then tells them that they are denying liability!  

Now don't get me started on how you can deny liability when your client hits a parked car, admits fault, calls you from the lot to tell you he just hit someone, and you have pictures that we both sent you.  That's ridiculous enough.

But how the heck can you, twice, send out your adjuster to get an initial estimate, then to approve the actual cost before repairs, and then after doing so, deny liability??

Seems like a pretty d**n shady organization to me.