Bullet trajectories as determined by Taiwanese authorities are depicted below. Click for higher resolution.
The Philippine government gave contradictory excuses for the shooting. On the day after the killing, they said the fiberglass fishing boat’s operators were trying to ram the Coast Guard vessel and that the Coast Guard gunners were deliberately firing at the boat to disable its engine. The Ilocos-class Coast Guard vessel, at 35 meters (114 feet), was six times the size of the fishing boat. The fishing boat's engine, of course, would not have been in the crew’s quarters in the forward cabin. Furthermore, Taiwanese forensic investigators found no sign that the fishing boat had rammed anything.
One Philippine spokesman claimed that they were trying to disable the engine while the fishing vessel was trying to escape. Apart from the logistics of firing into the forward end of a fleeing vessel, international law forbids firing at a fleeing vessel unless it’s a warship in time of war.
As of this writing, Aquino has offered no real apology (just a lame excuse that it was all an accident), no offer of compensation to the family of the murdered fisherman, and no sign that he would welcome a joint investigation of the crime.