A murderous, spurned lover fatally shot his ex-girlfriend, then cruelly taunted her new boyfriend and several of her relatives — boasting that he was the “grim reaper” before getting killed in a gunfight with cops early Tuesday morning.

Vicious ex-con Dalton Branch — who also tried to shoot the other man in the love triangle — twice called his victim’s elderly aunt after gunning down Patsy Mohammed outside the casino at Aqueduct Raceway in Queens.

“He told me I should prepare myself to bury my niece,” Rosemarie Guilford, 75, said at the Brooklyn home she shared with Mohammed.

“Then he called back and he told me: ‘I gave it to her good, she’s dead so prepare yourself…I could come and burn your house down.”

“I couldn’t say anything. What am I going to say? I was just listening to the guy rant and rave,” she added.

The hulking killer — who got shot while trying to grab a cop’s gun in 1983 — also sent a series of text messages to other Mohammed family members, saying “I’m the grim reaper” and vowing “I’m not going down easily” following the 2:20 a.m. attack, law-enforcement sources said.

Branch, 51, even sent texts to Mohamed’s new boyfriend — who was Branch’s former boss — repeating the “grim reaper” bluster and adding: “How you like that p—y now?” sources said.

Cops used cell-tower information to trace Branch to an East New York parking lot where he opened fire when three members of the Queens Warrant Squad rolled up shortly before 6 a.m.

The cops shot back, killing Branch in a furious exchange of gunfire that left him with 15 bullet wounds, NYPD Chief of Detectives Robert Boyce said.

A cocked and blood-stained .380-caliber pistol was found at the scene, along with a spare magazine, a box of bullets and Branch’s cell phone, Boyce said.

“He wanted to go out in a blaze of glory,” a source said of Branch.

Surveillance video of the Resorts World Casino parking lot shows Mohammed driving up and waiting outside her car for about 10 minutes for Kenneth Hickman, 51, a supervisor for a bus company that shuttles gamblers there, sources said.

The couple embraced and made out, then chatted until Branch drove up in a rented, white Dodge Charger and started shooting, sources said.

Boyce said Mohammed, 55, scrambled into her car, where Branch repeatedly shot her.

Branch then got back into his car and chased Hickman around the lot, repeatedly firing through the open windows as Hickman ran and hid behind parked cars, sources said.

Branch finally gave up, drove back to Mohammed’s car and shot her repeatedly until he ran out of ammo and drove off, sources said.

Branch and Hickman formerly worked together at the bus company, Trans Express, where Branch was a driver, sources said.

Branch had a lengthy arrest record dating back to 1982, and he was shot by a cop in 1983 when he tried to grab a gun from the cop’s partner, Boyce said.

He spent about three years in the slammer for that, and almost three more years for a 2002 weapons-possession bust in Brooklyn.

Boyce also said Branch served “some jail time” for a shooting a man in the leg following a 1989 fight near Times Square.

Mohammed’s aunt described him as a “very brutal type of guy,” adding: “It’s one of those things that you all write about all the time, a broken relationship and one person can’t deal with it and decided this is how it is going to play out.”

Her ex-husband, George Guilford, 81, also said Branch was “controlling” toward Mohammed, saying: “Wherever she was, he wanted to be.”

A family friend said Branch called him “right after” shooting his ex and confessed, saying: “I did it. I’m not going back to jail.

Eric Woodruff, 58, also said Branch had earlier been “ranting and raving” about Mohammed because she had dumped him.

“She kept pushing his buttons, kept calling on his cell phone and hanging up. She pushed the last button,” Woodruff added.

“He had a lot of tension built up. He exploded.”