A Philadelphia-based scientist has died after he and his fiancée were shot by a dozen AR-15-blasting gangsters in a seemingly random attack while vacationing in Puerto Rico, according to reports.

DuPont chemist Omar Padilla Vélez, 33, was driving wife-to-be Kelly Crispin, 31, back from a night out clubbing in San Juan on Jan. 3 when he mistakenly took a wrong turn, Crispin told the Philadelphia Inquirer.

A dozen masked men carrying AR-15-style rifles suddenly surrounded the car — and opened fire when Vélez tried to drive past, his fiancée said.

“I’ve been shot,” Vélez cried, according to Crispin, who was also hit in the hand and shoulder by some of the bullets piercing their car.

One of the gang members took Crispin’s phone as she tried to call for help — while another seemed to regret attacking a woman, she recalled.

When the shooters — who did not take anything — fled, a friend who had been with the couple drove them to a hospital as Crispin applied pressure to her partner’s wounds, which included a bullet wound to his head.

The Puerto Rican-born chemist, who was in Puerto Rico to celebrate the new year with relatives there, was initially stable enough for his sweetheart to visit him two days after the attack, she said.

“He told me that he loved me, and I told him that I loved him, too,” she said. “And he said, ‘I’m so sorry.’ Then he fell asleep.”

Vélez soon suffered a catastrophic stroke and died.

San Juan police told the grieving bride-to-be that the attack was a random show of force by a gang known to control the tourist area. No arrests have been made, according to the Inquirer, which said police did not return calls for comment.

Vélez had left Puerto Rico in 2015 to earn his Ph.D. at Cornell University, before moving to Philadelphia in 2022 to work as a senior scientist for DuPont in Wilmington.

He met Crispin about three years ago at their best friends’ wedding, and they got engaged in September.

“We had just made this decision to spend the rest of our lives together forever,” Crispin said.

“It just feels so cruel that this was taken away.”