You don't get it. To understand those guys, you need to understand the pirate mentality. They couldn't care less about law enforcement or the crew. They care more about capturing the boat intact. Shooting the engine reduce the value of the boat and it could cause a fire that result in the loss of the boat. Worse, you would have to tow the ship and that slowed you down and allow the *real* law enforcement (i.e. Taiwanese Coast Guard) to catch up. Boats usually are the whole asset and livelihood of the fishermen -- hence the ransom will not exceed the value of the boat. And if the ransom cannot be paid, then the boat is confiscated -- more for the pirates. Hence they would rather kill some of the crew to stop the boat rather than damage the boat. They are simply greedy.
Maybe they simply wanted to kill everyone and loot the boat - so sinking it would not be a good option. Ramming it might cause it to sink, and they can't board it while it is taking evasive maneuvers. So the best they can do is shoot it up in the hope that people on board would all be killed or overwhelmed into stopping. Then they can board the ship and do whatever they want.
After they arrested everyone who is alive they can sink the ship if they want, leaves no evidence and forcing the detained to sign documents, then publish their side of the story. The Taiwanese government won't be able to act too tough while the fishermen are still detained.
This could all start from the PH CG demanding to board the ship and search, and refused by the Taiwanese boat, for lack of a good reason on the open sea. If the families have to pay heavy fines for the detained fishermen the CG crew might gain benefit out of it.
I cannot help but think in an ugly way, there is very little other reasons to explain their actions.
I think all mainland fishing boats should have Beidou capabilities installed, Beidou allows text messages to be sent and that might mean a lot of difference in future situations like this.
