FBIの者ですが。

English Translation

I’m from the FBI.

Tip: Some of you may wonder why the Japanese sentence is ended with が. This is actually very natural and common in Japanese.
The full sentence versions are

(私は)FBIの者ですが、お時間いただけませんでしょうか? = (lit.) I am a person belonging to FBI, but can I squeeze your time (to ask some questions)?
(私は)FBIの者ですが、少々よろしいでしょうか? = (lit.) I am a person belonging to FBI, but may I quickly have a word?

The latter phrases are obvious in the context, so we often drop them.