The Long Island native who died saving students in Florida last week gave his fiancée specific instructions about his funeral — should he ever die in a school shooting, the weeping woman said Sunday.

Hero teacher Scott Beigel once told fiancée Gwen as they watched coverage of a school shooting on TV, “Promise me if this ever happens to me, you will tell them the truth — tell them what a jerk I am, don’t talk about the hero stuff,” the grieving woman said through tears during Beigel’s funeral at Temple Beth El in Boca Raton, Fla.

“OK, Scott, I did what you asked,’’ the tearful woman continued. “Now I can tell the truth. You are an amazingly special person. You are my first love and my soulmate.’’

Beigel, a 35-year-old geography teacher who was born in Dix Hills, Long Island, had unlocked his classroom at Marjory Stoneman Douglas High School to let in some students during Wednesday’s deadly mayhem — then got nailed by a bullet while trying to lock the door again to keep out alleged killer Nikolas Cruz.

His maternal uncle, Mark, responded to reports that the FBI had received tips about Cruz that it failed to follow up on, calling out the “epic failure of law enforcement agencies — especially at the top — that are responsible for the loss of these 17 lives.’’

Beigel grew up in Dix Hills before attending the University of Miami, according to his obituary in the Florida Sun-Sentinel. He also coached the Stoneman Douglas cross-country team and was a counselor at Starlight Summer Camp in Pennsylvania.

He was inspired to become a teacher after he started attending the camp at age 7, the paper reported.