Joan Chouest Attacked by Pirates Off Nigeria

Just received this. Anyone know any details?

REGION: Gulf of Guinea DATE ISSUED: 2016-04-14---------------------------------------------------On 13-APR-16 at 02:33LT, the US-flagged JOAN CHOUEST MPN-Contracted tug was boarded by armed pirates in approximate position 04 14 00 N, 08 01 00 E, 15nm off Akwa Ibom, Nigeria, 23nm offshore, in the Gulf of Guinea, exact position not known. The tug was towing the Greek-flagged crude oil tanker EXPLORER when she was attacked. A service technician was shot in the right foot. The attackers escaped at the intervention of a security vessel. MPN arranged security and medical response.While navigating the Gulf of Guinea mariners are urged to use extreme caution and maintain max CPA with any craft acting suspiciously. Furthermore, mariners are encouraged to review and employ the latest Best Management Practices (BMPs), as appropriate for the operational environment.

Why is it we cant just shoot these guys?