The 12-year-old son of a retired NYPD sergeant happily shook his neighbor’s hand before hopping on his bike to pedal to the bodega where he was fatally shot — the innocent victim of a possible gang beef, the resident and law-enforcement sources said Sunday.

Tragic Jacob Freytes was struck by a stray bullet during the senseless shootout in a gang-infested area of The Bronx on Saturday, leaving his family and neighbors distraught over the loss of the bubbly boy.

“His mother is destroyed, completely destroyed,’’ weeping family friend Carmen Uriza said Sunday.

Jacob’s grieving 12-year-old pal Marlyn Rosario lamented, “ He was at the wrong place at the wrong time.”

Marlyn’s mother, Miledy Rosario, said Sunday that she had just given Jacob the bike Friday.

“I bought a new bicycle for my daughter, and I asked him, ‘Hey, do you want [her’s]?’ ” she said.

“He said, ‘Oh, thank you so much. 
I’m gonna talk to my mom.’ And they gave him permission to have the bicycle. … And, you know, he was really happy,” she said.

Neighbor Walter Calon, 56, recalled, “I saw him just before he left.

“I shook his hand and said, ‘Look out for your little brother and sister.’

“And then less than a half-hour later, I got a call from my mom and I just dropped the phone right out of my hand,” Caolon said.

“I ran back and everybody in front of the building was crying,” said Calon, 56. “Everybody on the block was crying.”

Jacob had pedaled to Wanda Deli Grocery at Elliott Place near the Grand Concourse shortly before 5 p.m. when he was fatally struck by a stray bullet as a possible gangbanger opened fire at rivals, sources said.

The Mount Eden neighborhood is known territory for the violent Trinitarios and Sev Side Pinni street gangs, and sources said police are probing if the crews were behind the shooting.

The suspected gunman got into a dispute with another group outside the bodega, with the beef escalating when the shooter pulled a gun and opened fire, sources said.

Heartbreaking security footage shows the youngster stumbling back into the shop clutching his chest before he collapses.

The tragic youngster’s father is retired NYPD Sgt. Jesus Freytes, who once worked in the Bronx precinct where the shooting occurred, sources said.

He and Jacob’s mom “met while he was on duty,” another neighbor told The Post. “It was the kind of romance everyone talked about. A cop and a girl from the hood.”

The dad is as “devastated’’ as the mom, neighbors said.

His mom so distraught that neighbors said she was staying at a local hotel because she could not bear the pain of being home.

“She’s not OK,” Jacob’s aunt sobbed. “She can’t come down here. She can’t, I’m sorry.”

Julio Lopez, who said he was like an uncle to Jacob, on Saturday recalled how joyful the child was.

“I saw him today. He was playing with a tennis ball and a baseball bat. At around 4:30 p.m., I pulled up and he was right here playing. And then he jumped on his bike,’’ Lopez said.

“He was adventurous. He was a free spirit. He was different. He lived on his own terms, and he was only 12.

“I was him this morning, he was the family dog. He got a dog named Max. He was happy. He was chipper. He was saying hi to the guys up the block. He showed respect. He was a good kid.”

Calon added, “He always saluted me.

“Last week, my wife came up, and he said, ‘I like your wife!’ I smiled and said, ‘Yeah, I like her, too,’ ” the local said of Jacob.

“He was a bright kid. He played sports — he’s always playing here in the front court.

“I saw him grow up. He’s a good kid. I don’t understand.’’

On Saturday, Jacob pedaled to Wanda Deli Grocery at Elliott Place near the Grand Concourse shortly before 5 p.m. when he was shot, possibly during a gang beef.

The Mount Eden neighborhood is known territory for the violent Trinitarios and Sev Side Pinni street gangs, and sources said police are probing if the crews were behind the shooting.

The suspected gunman got into a dispute with another group outside the bodega, with the beef escalating when the shooter pulled a gun and opened fire, sources said.

Heartbreaking security footage shows the youngster stumbling back into the shop clutching his chest before he collapses.