Fernando Jimenez, 41, pleaded guilty to shooting not only the teen, but also his girlfriend and her other son at an apartment complex in Somers.
His girlfriend's son, Michael Raimondi, was killed in the shooting.
After an all-night manhunt, police later found Jimenez, who is undocumented, hiding in a Putnam County realtor's office.
In court on Thursday, Christina Raimondi spoke about her slain son during a victim impact statement.
"I miss his voice, his hugs, his smile, his amazing personality. I do not understand why this had to happen to him" she said.
Jimenez had agreed to a plea deal and will be sentenced to 37 years in prison.
ALSO READ: Man behind triple shooting that left 15-year-old dead gets 37 years
Man pleads guilty to deadly triple shooting of girlfriend and sons in Somers
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