No one knew anything was wrong inside apartment 408 until Jefferson Parish deputies arrived early Sunday morning and found a pregnant Katherine Martinez dead on the kitchen floor.

But things had gone terribly wrong hours earlier.

Martinez, who was reportedly being stalked online by her jilted ex-boyfriend, Emilio Calderon, was stabbed and strangled, allegedly at his hands, after he became enraged that she was pregnant by another man, Jefferson Parish Sheriff Newell Normand said Wednesday.

Calderon, 29, was arrested Wednesday and confessed to investigators that he argued with Martinez about the fact that her child was not his, Normand said.

He faces charges of second-degree murder and first-degree feticide.

When Calderon found out Martinez was carrying another man’s baby, he went to her apartment in the 600 block of Whitney Avenue in Terrytown on Saturday, buried a knife in her three times, then gripped his hands around her neck, slowly squeezing the life out of her as she tried in vain to fight him off, Normand said.

By the time her mother arrived there around 1 a.m. Sunday, Martinez and her unborn child had been dead for more than 12 hours, Normand said.

Calderon had allegedly been stalking Martinez through social media using a fictitious name, the sheriff said.

While there apparently was trouble between the two, Normand said, Martinez never filed any police reports against Calderon. Instead, she talked to her family.

Normand said investigators know of no previous violence between the couple or criminal record for Calderon.

While Martinez was stabbed three times, an autopsy found the cause of her death was strangulation, Jefferson Parish Coroner Gerry Cvitanovich has said. Martinez’s unborn daughter was not stabbed but was unable to survive the attack.

Calderon, who works in Larose, was picked up Wednesday at his job by the Lafourche Parish Sheriff’s Office and held there until Jefferson Parish authorities arrived to take him into custody.

He hung his head and said nothing as detectives marched him past reporters into a JPSO bureau Wednesday afternoon.

Follow Danny Monteverde on Twitter, @DCMonteverde.