We all want answers - but- lest not forget- at the cost of jeopardizing an investigation- especially combined with the ATF, FBI, and Secret Service.
Additional tidbit- I am sure being on embassy row in close proximity to VP, other foreign dignitaries, etc, has a lot to do with secret service being involved, but I do know for a fact that the secret service also gets involved when financial crimes are committed- link for reference:
http://www.secretservice.gov/faq.shtml#faq5
Not that it means anything but its pretty cool to read up on all that they do.