Here's all I know about him:
1. He was a spy in the Ministry (when Voldie was rising to power--again).
2. We don't know what his first name is.
3. He was one of the original DE (as in he was around for both wars).
4. He was witness to Snape killing Dumbledore.
5. He was the Head of Magical Law Enforcement (DH).
6. He is "defeated" by George and Lee.
7. It is presumed that he was either sent to Azkaban or killed--this is never answered by JKR.
If anyone could fill me in on more information, it would be very much appreciated.