A former Kendall bank executive who gunned down his ex-wife’s unarmed husband, lost his bid at immunity under Florida’s controversial self-defense law.

A judge Wednesday rejected Cristobal Palacio’s claim that he was defending himself against Paul Winter, who was shot six times — including twice in the back in October 2008— as Palacio’s 7-year-old twins watched in horror.

The judge’s ruling means that Palacio, 46, will face a jury trial next week for first-degree murder.

Palacio and ex-wife Jennifer Winter had undergone a bitter divorce that culminated in September 2007. Afterward, she married Paul Winter, a British-born graphic designer she met online.

Palacio claimed Winter spent months tormenting him, twice putting a gun to his face and frequently using profanity against him. The confrontations, Palacio claimed, took place during custody visits.

But Jennifer Winter testified Wednesday that her husband never owned a gun and was a peaceful “nerd” who avoided conflict. She also said her jealous ex-husband blamed Winter for their breakup.

Paul and Jennifer Winter had gone to Palacio’s home to drop off the twins for a week of court-appointed visit. Palacio claimed Winter charged at him in the driveway, reaching for what appeared to be a gun.

“The look on his face. The anger on his face, his veins were popping out,” Palacio testified. “He looked like he was going to kill me. I saw him going for a gun at the same time. I knew I was basically dead if I didn’t defend myself. He was coming at me full speed.”

Jennifer Winter said Palacio was the aggressor, charging out of the house, cursing and screaming.

“He just smiled. He grinned like he had just won the lottery. With his left hand, he pulled up his shirt, and with his right he started pulling his gun,” Jennifer Winter tearfully told the judge.

“I said, ‘Oh My God Paul, he has a gun.’ By the time those words were out, the first shots were being fired.”

Miami-Dade homicide Detective Juan Segovia also testified Wednesday that Palacio admitted he was mad at his ex-wife, and that he denied ever having been threatened by Winter in the past.

Jury selection begins Thursday in front of Circuit Judge Leon Firtel.