From what I heard it was the Navy Seals that rescued him. Pirate one was on board the ship talking ransom. Somehow the captain knew enough to jump off the life boat and the Seals or whomever was in the water shot the other three pirates before they could fire on the Captain.
The one on board the ship will be brought to the US and tried for piracy. The NY field office of the FBI is responsible for the case against him as they handle crimes against US citizens in Africa.
I am so happy for the Captain, his family, crew and the people he works with. That he was safe.
**edit now the Navy is saying they felt the ships captain was in danger so the Seals took out the pirates. The captain didn't have to jump off the boat to get away.