Matthew Mandap, a former U.S. Navy personnel from Hancock Avenue and Bowers Street, was charged with the death of Mario Vargas Jr., 20, also of this city.

The charge was upgraded after Vargas, a Hispanic, died at the Jersey City Medical Center on Tuesday morning, according to Hudson County Prosecutor Edward DeFazio.

Mandap surrendered to police and is being held at the Hudson County Jail in Kearny on $500,000 bail with no 10 percent option, DeFazio said.

DeFazio said Mandap, who was born in the U.S., recently left the U.S. Navy. His father, Romie, is a native of Pampanga, Philippines, and is running a deli.

The incident reportedly happened inside Mandap’s third-floor apartment on Nov. 20. Mandap hit Vargas once in the head with a wooden bat, knocking him to the floor, then hit him a second time — possibly when Vargas was unconscious, according to The Jersey Journal, quoting De Fazio.

But Mandap’s brother, Philip, said Mandap told him he was trying to defend himself and his friends after Vargas tried to break into their apartment after being kicked out of a party.

DeFazio confirmed to The Jersey Journal that Vargas was with the group who broke into the building and into the apartment.

Philip Mandap, who wasn’t present during the attack, said his brother told him that Vargas was among a group of men armed with baseball bats who broke through the building’s two front doors and smashed into Mandap’s apartment.

The apartment door appeared dented and misaligned, and was closed with a padlock, The Jersey Journal said. A shattered TV and broken glass could be seen, it added.

Philip Mandap said his brother told him he was in a relative’s apartment with his sister and grandmother when he heard people breaking through the building’s two front doors.

He said Mandap told him he called 911, but then heard noises coming from his third-floor apartment and ran upstairs with a baseball bat.

Mandap saw Vargas and others trying to break down a door in the apartment to reach other people from the party, Philip Mandap said.

Philip Mandap said his brother was surrounded by the intruders, but fled when they heard sirens, leaving only Vargas.

He said Mandap’s roommate came out of the room where he was barricaded and, when Vargas lunged at him, Mandap hit him with the bat. Philip Mandap said his brother told him Vargas then lunged again, this time at him, and he hit him a second time.

DeFazio said investigators believe Vargas was rendered unconscious by the first blow and was defenseless on the floor when hit the second time.

Vargas may have been trying to calm the situation when he was attacked, DeFazio said. That’s the scenario described by the friends and relatives of Vargas, who worked as a clerk through the On Target employment agency, the The Jersey Journal said.

But friends and relatives of Mandap expressed disbelief that he would commit such a crime for no serious reasons. “He was an altar boy, very polite, very resourceful and responsible,” according to close friends of Mandap’s late mother, Filipinas (Fay), who died of cancer in the mid-90s.

“He gave his mother so much joy until she died of lung cancer. He was with the U.S. Navy and he comes from a decent family.”

DeFazio said Mandap is facing a maximum sentence of life in prison if found guilty.

He said the case will be presented to the grand jury early next year. He added that Mandap’s family expressed intention to hire a private counsel.