Towing Issues: diesel fuel, tow truck driver, tow company

Question
My husband broke down on the fwy, he figured he ran out of gas but didn't know for sure because his gauge is broken.  He was sure he was pretty low going by his mileage.  He called AAA told them he needed gas and that he used unleaded.  Tow truck driver came, filled up his tank with 2 gallons.  My husband drove off, it sputtered and smoked, etc.,  and he had to pull over, call AAA again and get it towed to our mechanic ($65 tow bill).
Our mechanic called us and said the tank had diesel fuel in it. Obviously the tow truck driver put the wrong fuel in.  Everything had to be drained, etc.  So we now have a tow truck bill, gas bill (2 gallons diesel) and a mechanics repair bill.
First AAA said they would pay for the costs, now they say we have to go after the contracting tow company.  
Any thought who's fault this is and who we should go after for the cost?

Answer
Well, from what AAA policy is on this happens to be this way..

They will help you mediate the dispute between the member and service provider..

Now I have to say accidents and mistakes happen and I am not saying that its common to make that mistake it does happen..

Most tow trucks are carrying 2 cans for fuel, one for gas and one for diesel now...  It might of been that the cans were filled wrong.

Now I would contact the towing service which provided the service and talk to they about it. They will usually help you with the problem (remember asking not demanding will work better) Most towing companies know that mistakes happen..

As a side note here, most vehicles now have the fuel pump and gauge assembly mounted in the tank at the same place...
Running a vehicle low or out of fuel can damage the fuel pump as it uses the fuel to cool the unit while working...
Running out of fuel can damage the fuel pump to where it will fail in the future...