The “deeply obsessed” gunman who fatally shot his ex-girlfriend’s 19-year-old nephew in East Harlem texted his one-time love a day after the killing, blaming her for the bloodshed, prosecutors said Saturday.

“You know it’s all your fault and it’s only the beginning of my mission,” Jose Rodriguez texted his ex-girlfriend following the Wednesday morning shooting inside an apartment on E. 112th St. near Third Ave., part of NYCHA’s Jefferson Houses, prosecutors said at his arraignment in Manhattan Criminal Court.

Rodriguez, who is homeless, pushed his way into ex-girlfriend Melidy Adega’s second floor apartment about 3:30 a.m., pulled a gun and started shooting, the horrified woman told the Daily News.

“He took out his gun and he shot, pow, pow,” Adega, 38, said Thursday.

Ramon Alvarez, Adega’s nephew, also lived in the apartment and ran into the room to see what was going on. When he tried to intervene, Rodriguez killed him, prosecutors said.

“[He] then tried to kill his former partner by shooting at her, of whom he had become deeply obsessed,” prosecutors said at Rodriguez’s arraignment.

Adega said Rodriguez was shooting in the dark when he hit Alvarez in the abdomen. The teen and his girlfriend were expecting a baby boy next month and planned to celebrate the arrival at a shower scheduled for this weekend, relatives said.

After shooting Alvarez, Rodriguez turned and pointed the gun at Adega’s face, but the woman grabbed the barrel before he could fire off another shot, she recalled. She was grazed in the shoulder.

Rodriguez fled the area on a CitiBike. A few hours after he sent the threatening text to Adega Thursday, cops located him in the Bronx and took him into custody, charging him with murder and attempted murder.

Before moving in, cops spotted him chucking away a silver revolver, which investigators believe he used in the shooting.

Rodriguez has 27 prior arrests “spanning multiple decades,” police and prosecutors said. Over the years, he has given police six dates of birth, ten addresses and two Social Security numbers, prosecutors said, arguing that he was a definite flight risk.

A judge ordered Rodriguez held without bail.

With Nicholas Williams