The 13-year-old son of slain NYPD Officer Ralph Ramos took to Facebook hours after losing his beloved father to an anti-cop gunman.

“Today is the worst day of my life,” young Jaden Ramos posted Saturday night.

“Today I had to say bye to my father. He was there for me everyday of my life, he was the best father I could ask for. It’s horrible that someone gets shot dead just for being a police officer. Everyone says they hate cops but they are the people that they call for help. I will always love you and I will never forget you. RIP Dad.”

Fewer than two weeks ago, Jaden celebrated his father’s birthday, not knowing it would be for the last time.

“Happy birthday to the best dad in the world,” the teen wrote Dec. 9, accompanied with a photo collage of his family, with the boy’s arm slung over his dad’s shoulder.

“You are always there for me even when it’s almost impossible. We have so many good times it’s not even funny, I love you so much…..How does it feel to be 40? You’re getting old dad but you still look good. Hope you have the best birthday, you deserve it,” the post continued.

Officer Ramos and his partner, Wenjian Liu, 32, were shot execution-style as they sat inside a patrol car in Bedford-Stuyvesant, Brooklyn, at 2:45 p.m. Saturday.

The shooter, Ismaaiyl Brinsley, 28, was on a mission to kill two cops — apparently in a twisted bid to avenge the deaths of two black men, Michael Brown and Eric Garner, at the hands of white cops — and declared his intent on Instagram.

“I’m putting wings on pigs today. They take 1 of ours… let’s take 2 of theirs,” Brinsley posted.

The gunman riddled the marked patrol car with bullets before fatally turning the gun on himself.