Guilty plea to killing ex and son, 4

A BRONX man who strangled his ex-girlfriend and their 4-year-old son pleaded guilty to the killings Tuesday.

Isaac Duran Infante, 24, admitted murdering Felicia Barahona, 36, and little Miguel inside their W. 153rd St. apartment in Manhattan on Dec. 22.

Infante confessed to investigators that Barahona was “still gasping for air and fighting for life,” when she screamed for their son to call 911, according to prosecutors.

Barahona was Infante’s science teacher at DeWitt Clinton High School when they met, and started a sexual relationship in 2011, when Infante was 18 years old. Five years later, her former student used an electrical cord to end her life.

Once Barahona was dead, Infante set his sights on his own child, whom he strangled and left “lying face-down in a bathtub filled with water,” prosector Nicole Blumberg said.