A 34-year-old man was arrested in a 2015 execution-style slaying of a mother-of-five in a Bronx apartment building stairwell, authorities said.

Lasalle Herman, of Harlem, was cuffed Tuesday afternoon and faces a murder charge in connection to the March 4, 2015, slaying of Michelle Cox, 41, in her building on Webster Avenue near Alden Place in the West Bronx, police said.

He was being held in federal prison Wednesday afternoon, cops said.

The deadly shooting may have been gang-related, police sources said Wednesday.

It was unclear whether Cox knew her killer.

“She just left to go to the store,” Cox’s long-time partner, Ryann Solomon, 40, told The New York Times the day after the slaying. “I actually saw her there in the staircase.

“Everybody loved her,” Solomon added. “I don’t know who would do this to her.”

Cox had two daughters, 8 and 17, and three sons, 19, 24 and 27, The Times reported.

“I was told she was killed in these staircases,” Cox’s grieving daughter Jazmine Ghee told the paper as she sat on one of the steps.

Cox, a security guard, had planned to apply for a new job at a packing plant in Hunts Point the day after the shocking murder, Solomon told the paper.

Cox had a history of her own run-ins with the law – with more than 20 total busts for prostitution, assault and drug offenses, the paper reported.

Herman’s arraignment was pending in Bronx Criminal Court Wednesday.