An NYPD cop tracked his wife and her young new lover to a hotel — then fatally shot the man before killing himself in the horrific love triangle gone awry, law enforcement sources told The Post on Monday.

Crazed off-duty Officer Sean Armstead, 36, had followed spouse Alexandra Vanderheyden, 35, and her 20-year-old beau, Edward Wilkins, to a La Quinta Inn in upstate Wallkill around 10:30 p.m. Sunday, sources said. 

Vanderheyden told investigators she believes that Armstead tracked her through her cellphone, sources said.

Armstead then chased the pair out of the hotel, and the illicit lovers hopped in their car to flee, with the cop in his own vehicle in close pursuit, sources said. 

The cuckolded hubby eventually slammed into their ride near the intersection of Route 211 East and Tower Drive outside a Buffalo Wild Wings, according to sources. 

Wilkins then got out of the couple’s car and ran off, but Armstead followed him and unloaded his weapon at him, firing off 16 rounds, sources said. 

The younger man was fatally struck in the back and head, according to sources. 

Then Armstead reloaded his weapon and fatally turned it on himself, sources said. Vanderheyden was unhurt, sources said.

A pool of blood could still be seen outside the restaurant Monday morning.

“It happened outside,” a Buffalo Wild Wings manager told The Post. “The night manager told me she kept everyone inside and locked the doors. We closed early last night. I don’t even think they came in here.”

Armstead was appointed to the NYPD in July 2011 and worked in PSA 8, which patrols NYCHA developments in a section of the Bronx. 

Back in 2016, Armstead was assaulted and robbed of his wallet — containing his NYPD identification card — while walking his dog in Harlem, according to police sources.