CHICAGO --A senior at Gage Park High School is the twentieth Chicago Public Schools student to be killed by violence this year.Eighteen-year old Salvador Contreras was shot to death early Saturday morning. Police say he was standing along the 5800 block of South Hamlin when a car approached. Contreras apparently argued with someone inside the car and was shot. Of the 20 students killed this school year, he is the eighteenth to be shot to death. "These are quick, snap decisions that happen that have such a phenomenal effect. We have to do something now to get guns off the street," said Rufus Williams, Board of Education president. "Everybody loves Salvador because he was very special," said Giovanny Moctezuma, friend. Counselors will be at the school next Monday when students return from spring break. Police have not made any arrests.