The parents of critically wounded American protester Tristan Anderson called on the police Monday to launch a criminal investigation into the border policeman who shot a high-velocity tear gas canister that hit their son on the forehead in the Palestinian village of Ni'lin earlier this month. "We want to know the truth of what happened, and we want justice for our son," Anderson's father, Michael, told reporters at a press conference he and his wife Nancy held in Jerusalem. They had flown to Israel from their home in Grass Valley, California, after their son was hurt, and have been with him since at Tel Hashomer Hospital. "Tristan is in the hospital, unconscious. We do not know if he will recover, and if he does, we do not know what abilities he will ever regain. He has already had three operations and will need three more and long-term rehabilitation," Nancy said. "We are are scared and in shock. This is only the second time we have left the hospital since we arrived in Israel," she added. "What we want to ask is that the Israeli government take full public responsibility for the shooting of our son," Nancy said. The IDF, which commanded the Border Police operating that day in Ni'lin, has launched a high-level investigation into the incident. Anderson, 37, was wounded at 4:30 p.m. on Friday, March 13, after Border Police dispersed a protest against the security barrier, held on the outskirts of the village. Anderson had participated in the protest. A Border Police source told The Jerusalem Post that security forces had been dealing with a disturbance at the time, and described the casualty as a "sorrowful and unfortunate" result of a rare accident. The source said the canister struck the ground after being fired by Border Police, and then ricocheted back up into the air, striking the American protester in the head. "This is a sad event. The Border Police officers were dealing with a disturbance. The group facing them was made up of anarchists and Palestinian demonstrators," the source said. "A high number of tear gas canisters are fired, and for such a thing to happen is very rare. It has never happened before, and I hope it never happens again," the source added. But the human rights group B'Tselem has said they have video footage of other incidents in which border policemen have thrown these high-velocity canisters at demonstrators. In one instance, a 13-year old Palestinian boy was wounded. According to Anarchists Against the Wall, which helped organize the press conference for the Andersons, these canisters have only been in use since December 2008. B'Tselem has written to the military advocate-general, Brig.-Gen. Avihai Mandelblit, and asked that he forbid security forces from firing them directly at protesters. Attorney Michael Sfard, who represents the Andersons, downplayed the importance of the IDF investigation, which he said jeopardized the possibility of a criminal procedure. The "command inquiry" that the IDF has launched is not about finding liability but rather investigating operational flaws, said Sfard, adding that this type of investigation did not have the same investigatory power to collect evidence as a criminal one and would allow the Border Police to coordinate their testimony. Sfard said his office had filed a complaint with the police to demand a thorough professional and unbiased independent investigation. The border policemen who threw the canister at Anderson were not under any threat, nor was the barrier, he added. The Border Police, he charged, had acted in violation of the rules of engagement of such weapons. According to B'Tselem, Anderson had been shooting photographs at the time he was hit. Jonathan Pollak of Anarchists Against the Wall added that Anderson had fractures on the right side of his forehead, a collapsed eye socket and severe brain trauma. Large portions of his frontal lobe had had to be removed, Pollak said. Michael Anderson said that his son, who lives in Oakland and was on a break from his work in California setting up conventions, was now in a medically induced coma. "Tristan has always been interested in how societies in conflict resolve their issues," said Michael, reading from a handwritten statement. "He has gone to many dangerous places. He went to Iraq during the Second Gulf War, and spent years in Central America right after the civil wars in El Salvador and Guatemala, advocating for social justice." When Tristan's girlfriend came to Israel on a birthright trip, he followed separately to be with her and to understand for himself what the Israeli-Palestinian conflict was about, Michael said. "It is ironic that the country in which he was shot was a democracy, in which it is supposed to be the duty of everyone to follow their conscience," he said. Nancy added that they had planned to meet Tristan in Europe once he left Israel. Since July 2008, four people have been killed by security forces at anti-barrier demonstrations in Ni'lin: Ahmed Mousa, 10, Yousef Amira, 17, Ghateb Khawaja, 22, and Muhammad Khawaja, 20.