A description like "ex US Agent" should be applied only to a person whose crimes were committed after their service as an agent and with no connection. It seems like this agent committed their crimes while working as an agent, and it would be more appropriate to describe them as "US Agent".
From the Reuters Handbook [1]:
>ex-
Make sure this prefix is hyphenated to the word it limits. Note the difference between a Conservative ex-minister and an ex-Conservative minister. Prefer “former” in written text , e.g., “Former Brazilian finance minister Jorge Braga was killed on Tuesday when...” “Ex-” may be used for brevity in headlines, e.g., “Ex-minister killed in Brazil air crash.”
The agent was still an agent when he performed the crime. It is disgenuous to say he's an ex-U.S. agent when he lost his title because of the incident.
You wouldn't say Ex-president Obama was impeached, that's just weird.
There are academic papers pointing out Reuters propaganda. http://blogs.roosevelt.edu/hsilverman/files/2011/11/Reuters-...
"Ex-Rep. Jefferson (D-La.) gets 13 years in freezer cash case" by the Washington Post [1]
"Ex-Congressman Gets 8-Year Term in Bribery Case" by the New York Times [2]
Each of these convictions related to things that happened while they were still Members of Congress. I'm quite happy that news outlets treat government officials the same way they'd treat a baseball player -- to do otherwise would just be a different form of "propaganda."
1. http://www.washingtonpost.com/wp-dyn/content/article/2009/11... 2. http://www.nytimes.com/2006/03/04/politics/04cunningham.html
Which would be relevant if the headline was about the commission of the crime, and not the conviction. He was not an agent at the time of his conviction, and had not been for some time. Reporting on the conviction, "former agent" or "ex-agent" is accurate, and anything else would be inaccurate.
> You wouldn't say Ex-president Obama was impeached, that's just weird.
Well, yeah, because an ex-President can't be impeached (unless they are now in another impeachable office.)
Impeachment happens while you are in office, and doesn't remove you from office (it is the formal initiation of a process which might, with conviction, result in removal from office.)
So, its not really a comparable thing.