Violent Shit III

The film opens with three men, Ron, Mark, and Peter abandoning their boat in the middle of the ocean and happening upon an uncharted island. After being captured by a gang of masked madmen, the three awaken to find themselves tied to crucifixes in the middle of a large militia camp. The trio are then introduced to the leader of the militia, Karl(better known to his men as the Meister). Karl and his hideously deformed father Karl Sr. oversee a series of gruesome executions before threatening the three trespassers with the death penalty. After spitting in Karl's face, Peter is put to death by having his right hand amputated with a machete and spears driven through his torso. The two remaining seamen as well as a traitor named Leon are turned loose in the forest to be hunted down by Karl's army of trained killers. After telling Ron and Mark of the Meister's horrific experiments, the three begin a search for weapons. Meanwhile, Karl's hired surgeon Dr. Senius is working on a breed of super soldiers that are going to replace the fallen ones in battle. After being disgusted with Senius's overall progress, Karl threatens Senius with death if he doesn't have the first batch ready within 24 hours. The next day, Leon tells the men of a safety bunker located on the far end of the island. Using handmade spears, the three kill two guards and severely injure one before taking off with their weapons. The surviving guard is punished for his disobedience by Karl when his spinal cord is torn from his anus with a large meat hook. Senius's first batch of super soldiers are turned loose in the woods. After a run in with the super soldiers(who better resemble zombies perhaps because of their hasty creation). Ron and Mark part with Leon who acquires the help of two comrades named Son and Giang. After quickly dispatching the soldiers, the three look for Ron and Mark. Ron and Mark meet their ends at a small pond when they are ambushed by a group of infantrymen. After their bodies arrive back at the base in poor condition(Ron's body split in half at the waist and the upper left corner of his head missing and Mark's head split in half down the middle)Senius orders that the soldiers responsible be punished right away. Karl lines them up and shoots them in the head one by one with a sawed-off double barrel shotgun. When it comes time to kill the last one, he runs, prompting Karl to shoot him in the leg. Karl then drowns him in a nearby puddle while Senius listens in and masturbates. Then Karl deploys a heavily trained gang of ninja assasins called the Black Demons to hunt down the remaining traitors and kill them. After briefly confronting the ninjas and killing them, Son, Giang, and Leon plan a full-scale attack on the camp at sundown. After reaching the main gates disguised as Black Demons with a prisoner, the two guards on patrol demand to know why Leon's still alive. Son and Giang then kill them both and advance on the camp. After slitting a soldiers throat, Leon steals his rocket launcher and oversees the fight from on top of a hill and assists the two others in killing off the soldiers. After running low on ammo, Leon joins Son and Giang on the ground below. Leon confronts a soldier wielding a machete and ends up getting impaled. With what energy he has left, Leon takes his killer's revolver and shoots him. After killing him, Leon drops dead. Son hides outside of Senius's tent and slices off his nose with a katana. Senius stumbles back into his tent where an unfinished super soldier asphyxiates him in his open torso and subsequently tears off his head. Senius is finished off when he runs outside headless and is shot by Giang with a submachine gun. Both Son and Giang find Leon's body and in an act of vengeance, hunt down Karl Sr. and Karl. When they are found trying to escape, the two Karls are confronted by Son and Giang, who kill their remaining troops. Son and Giang then engage in hand-to-hand combat with Karl Sr. and his son. After Son gets the best of him, Karl Sr. calls upon his bodyguard, a hockey-masked commando with a mechanical arm. After a short scuffle, Son detaches the bodyguard's artificial arm and impales him with it. Giang and Karl continue to fight until Giang back flips over him and rams his fist through his body from behind and places a hand grenade in his mouth. Karl's head explodes and he drops a rocket launcher. With the rocket launcher, Giang tells Son to get out of the way. After Son dives for cover, Giang proceeds to shoot Karl Sr. with the rocket launcher, exploding him. The two exchange a high five before the credits roll.

Question: Who shot Senius?
Answer: Giang