Update On Arizona Police Officer's Death

Last night a Chandler, AZ police officer was hot and killed and 2 other officers were wounded. In addition, two thugs were shot dead and 6 more were detained.
The name of the officer was just released. His name is Carlos Ledesma, 34 years old. http://odmp.org/officer/20484-police-officer-carlos-ledesma
From the Arizona Republic: During a Thursday press conference, Chandler officials said Officer Ledesma was killed during an undercover operation to purchase a large quantity of marijuana.
"(He) gave his life last night for this community," said Chandler Police Chief Sherry Kiyler
It's still unclear exactly how things went wrong, but officials said they're investigating the possibility that the drug dealers planned to rob the undercover officers. The officers had hundreds of thousands of dollars on them to make the purchase, officials said.
"They have not admitted that is what they were doing, but that is what we are looking at," said Phoenix Police spokesman Sgt. Steve Martos. Read more: http://www.azcentral.com/news/articles/2010/07/29/20100729chandler-police-officer-killed-reaction0729.html#ixzz0v7PxjTRJ
My question is why the officers had hundreds of thousands of dollars on them. I admit I don't know all that much about undercover police work, but officers having hundreds of thousands of dollars on them seems to be a bit unusual, if not unheard of to buy drugs. It is also strange that the officers were shot in Phoenix, not in Chandler.
Was this operation just a Chandler operation or was DEA involved?
Again, we don't know anything about the suspects- are there illegals involved? If so, all hell should break loose.