A man was shot to death outside a Bronx shelter as his girlfriend looked on in horror — and a teenager less than half his age has been arrested for the execution-style slaying, police said Wednesday.

Klint “Jason” French, 39, was gunned down outside Fordham’s Sammon Build Center shelter on Grand Ave. near W. 190th St. about 6:50 p.m. Tuesday, just moments after he stepped outside the shelter, where his girlfriend Katorah Davis lived.

“It was quick. Just like that,” Davis, 37, said on Wednesday. She was right behind French when he was killed. “I heard some shots ring out and I came downstairs and I saw him laying where the pole and gate is at the side of the building.”

Davis was captured on cell phone video, crouching over French’s body, hysterically telling responding cops to stay away from his body.

“Don’t touch him! Don’t touch him!” Davis pleaded with cops as they tried to inspect the body.

At least seven shots were fired, police said. The gunman ran off, but 18-year-old Iyahni Mcintosh was arrested nearby a short time later, cops said.

It wasn’t immediately clear why Mcintosh allegedly shot French or if the two men knew each other.

“He literally just walked out the door and he was shot,” Davis said. “He was a couple of feet away and that could’ve been anybody.”

“This man walks out of here all the time to go to work,” she said about her murdered boyfriend. “He isn’t on the corner or hanging around or nothing. He goes to work.”

A witness told the Daily News Mcintosh crept up to French and shot him at point-blank range.

“When he got close, he shot him twice,” said the witness, who declined to give her name. “When he fell down on the sidewalk, he shot him two more times in the head.”

French died at the scene.

Cellphone footage obtained by The News shows Davis screaming “Jesus!” and “Oh my f—— God!” as she sits beside his body, surrounded by police.

When a police officer tries to inspect the victim’s remains, Davis, dressed all in pink, puts her hands out, pleading, “Don’t touch him!” the video shows.

Mcintosh’s arraignment on murder charges was pending in Bronx Criminal Court Wednesday. The teen has prior arrests as a juvenile and lives in the Bronx about three miles from the crime scene, according to cops.

Davis said she doesn’t know why her boyfriend was targeted, and believes he may have been an innocent bystander.

“He doesn’t live here,” she said. “He came here to visit me. He doesn’t know a soul but me.”

French cut hair at a Brooklyn barbershop and came to the Bronx to visit her, Davis said. She said they had been friends for about a decade and dating for about a year.

“He was loving. He was respectful,” she said. “One of the sweetest, hardworking men I have ever known.”

She said French was also generous and tried to help people in his community.

“He would help the disabled and the homeless,” she said. “He was loved. He was truly loved. This wasn’t a man who was confrontational. He never involved himself in negative activity,”

Davis always appreciated the effort French made to maintain their relationship, she said.

“He was loyal to me. He would commute from Brooklyn and that’s a long ride just to see me,” she said. “He was always here on a regular basis.”

“I literally have his clothes on right now,” she said.