A Westchester County cop saw a Bronx boy leap from an overpass — and jumped after him to save his life, according to a report.

“Everything was happening so fast, and I think my adrenaline was pumping so high,” Hastings-on-Hudson police Officer Jessie Ferreira Cavallo told the Journal News.

The hero cop said she was driving to work Friday when she watched in horror as a 12-year-old boy climbed up over a guardrail on the Saw Mill River Parkway and tumbled several feet onto concrete.

She said she quickly parked on the shoulder, stuffed her pockets with first-aid materials and leaped after the boy.

“I just knew, when I looked down and saw him… I thought to myself, ‘He needs help. I need to help him,’ ” she said, adding that the boy “looked dead” and that the area where he fell was covered in blood.

At the time, making the jump to help the boy didn’t seem like a big deal, she said.

“I didn’t realize how high it was. It didn’t seem that high,” she said. “It was so fast, it was more like tunnel vision. I saw the boy, and I knew I needed to get to him. I didn’t see anything else.”

Another woman in a military uniform also stopped to lend a hand, Cavallo said, and together they put the boy in a neck brace and splint and checked his airway.

After some time, the boy opened his eyes, but wasn’t responding any other way.

Police and an ambulance transported him to Westchester Medical Center, where he was treated for a broken arm, broken nose and leg injuries, according to Westchester County Police spokeswoman Kieran O’Leary.

The boy, who is from the Bronx, had run off from an organization that serves children with special needs or emotional and behavioral issues in Yonkers called Andrus. Staff members followed him and were trying to speak to him on the parkway when he plummeted, O’Leary said. It is unclear how high the fall was.

“I just hope he’s doing well,” Cavallo said. “I just want to give him a hug.”