The deranged ex-boyfriend accused in the vicious ambush murder of his on-again, off-again girlfriend in a Harlem building was charged Tuesday – after whining to cops she had been his “entire life,” cops and sources said.

Luis Marquez, 41, allegedly knifed mother-of-four Carmen Lopez, 47, as many as “50 times” Monday when he attacked her inside her West 129th Street apartment building – where he heartlessly left her to die alone in the hallway as her two kids slept inside, authorities and sources said.

Marquez, of the Bronx, was apparently enraged with jealousy because the victim used him and didn’t make him a “priority,” the sources said.

Carmen Lopez, 47, was stabbed as many as “50 times” Monday when Luis Marquez attacked her inside her West 129th Street apartment building in Harlem.

He described Lopez — whom he’d dated on and off for about five years — as his “entire life” to police while in custody, though the two were no longer together at the time of the slaying, the sources added.

Building porter Lyron Middleton happened to be cleaning the staircase when he stumbled upon Lopez covered in blood and called 911, he said Monday.

Lopez was rushed to Mount Sinai Morningside Hospital, where she succumbed to her grave injuries, cops said.

Marquez’s charges came after he was initially brought to Lincoln Medical Center for a 24-hour psychiatric hold. Stephen Yang for the New York Post

Marquez being ushered by officials into a car outside the NYPD 26th precinct in Harlem. Stephen Yang for the New York Post

Surveillance footage – which Middleton couldn’t bear to watch but only listened to the audio – captured the moment the attacker ambushed Lopez after apparently waiting outside the elevator for two hours, sources and the porter said.

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“She was yelling out someone’s name as it was happening,” Middleton said of the footage. “They say, ‘Luis, Luis, Luis. Luis stop, Luis stop.’”

The kids, 10 and 18, were sleeping inside while their mom was brutally attacked, the sources said. 

Marquez, meanwhile, went to his home and rambled to his family repeating over and over that he had killed her, according to the sources. His relatives took the disturbed slasher to a local hospital, which is where police first took him into custody, sources said.

At the victim’s home Tuesday a woman who identified herself Tuesday as Zoila, Lopez’s sister, refused to talk besides tearful replies of “yes” when asked whether her slain sibling was a good woman, and whether she was hurting.

Surveillance footage captured the moment the Marquez ambushed Lopez after apparently waiting on the steps for two hours. Robert Mecea

Another woman who showed up at the building said in Spanish that Lopez was originally from the Dominican Republic.

A building superintendent told reporters Monday that Lopez had four kids, two who live with her and two who are older and live in New Jersey. 

“I don’t know how did this happen, because they are not a problem person, any one of them. They are nice [people], like our family,” the worker said.

Marquez’s charges came after he was initially brought by authorities to Lincoln Medical Center for a 24-hour psychiatric hold, according to the sources.