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A Northlake couple remained shaken and confused Saturday as they tried to cope with the slaying Friday night of their daughter and her boyfriend, which left an infant without a mother.

Alissa Cline, 17, and her boyfriend, Efren Ramirez, 22, were fatally shot by Cline’s ex-boyfriend, Isidro Vargas, 22, Northlake police said. They said Vargas then shot himself to death. Police said they suspect jealousy was the motive in the slayings.

“We never saw (Cline and Vargas) argue or fighting,” Alan Ruiz, Cline’s stepfather, said Saturday. “There was never anything confrontational or any threats made. (Vargas’) mannerisms were always subdued. We had no indication he would ever do anything of this magnitude.”

Cline and Ramirez were killed with a semiautomatic rifle at about 9:15 p.m. while outside in the 200 block of South Harold Avenue, police said.

The shots missed Cline’s 1-year-old son, Marc Anthony, who was sitting in a car parked in the driveway. Vargas was the child’s father, according to Betty Ruiz, Cline’s mother.

Alan Ruiz said Cline dropped out of Proviso West High School in Hillside last year after giving birth.

He said Vargas was living with his aunt in Melrose Park.

The Cook County medical examiner’s office said Cline and Ramirez died of multiple gunshot wounds, and Vargas died of a gunshot wound to the head.

Police said they received a call of a domestic confrontation at 9:15 p.m. No other details about the shooting were available.

Also Saturday, McCook police said they were investigating the possible homicide of an unidentified man who was found fatally shot at 4:30 a.m. Illinois Highway 171, just south of Joliet Road.