On June 24, 1993, Medellín performed a gang initiation in a park along with five others, Peter Cantu, Roman Sandoval, Efrain Perez, Raul Villareal and Derrick O'Brien. Two others, Frank Sandoval and Venancio Medellín, were present but did not participate in the initiation. The initiation involved the new member, Raul Villareal, submitting to beatings from the others. After this, the gang members remained in the park, drinking beer. At this time, 14-year-old Jennifer Ertman and 16-year-old Elizabeth Pena were taking a shortcut through the park to get home before curfew. They encountered the gang, and Medellín began talking to Pena. She attempted to flee, but he forced her to the ground. Pena cried for help and Ertman ran back to assist her. In response, Cantu and O'Brien pushed her down as well. Roman and Frank Sandoval chose to leave then. The remainder of the gang, as well as Venancio Medellín, took turns vaginally and anally raping the two girls. Afterwards, they were beaten, then the gang decided to murder the girls so they would not be identified as the rapists. Medellín killed one of the girls by using his shoelaces to strangle her, then crushing her neck with his foot. Other gang members strangled the remaining girl with a nylon belt, until the belt snapped.
Medellín, Villareal, Perez, and Cantu then congregated at Cantu's home, where he lived along with his brother, Joe Cantu, and sister-in-law, Christina Cantu. Christina Cantu questioned why Villareal was bleeding and Perez had a bloody shirt. This prompted Medellín to say the gang "had fun", and that details would appear on the news. He then elaborated that he had raped both girls. Peter Cantu then returned, and divided valuables that had been stolen from the girls. Medellín got a ring with an "E", so he could give it to his girlfriend, Esther. Medellín reported that he had killed a girl, and noted that he would have found it easier with a gun. Derrick Sean O'Brien was videotaped smiling at the scene of the crime. After the gang left, Christina Cantu convinced Joe Cantu to report the crime to police. Four days after the crime, the bodies were found in the park. They were badly decaying, and dental records were used for identification. The medical examiner corroborated that the cause of death was strangulation. All those believed responsible were ultimately arrested. Medellín gave both a written and taped confession