A monster ex-con on parole fatally knifed a mom of three at a Long Island gas station as stunned bystanders watched in horror, prosecutors said Sunday.

Michael McHenry, 40 — who had just been freed from prison in March — stabbed his 30-year-old girlfriend and home-health aide Juliann Bachmann in a violent frenzy outside a Speedway gas station in Yaphank shortly before 7:30 a.m. Saturday, according to authorities.

“She wanted to be friends with everybody, have love from everybody,” Bachmann’s heartbroken younger sister, Kristen, told about 50 friends and relatives gathered at a Sunday evening vigil for her slain sister at the Speedway. 

Michael McHenry in court for his arraignment Sunday. He’s accused of fatally knifing mom of three Juliann Bachmann outside a Speedway gas station in Yaphank. John Roca for NY Post

Juliann Bachmann, 30, was pronounced dead at NYU Langone Hospital. Facebook/Julie Mary

“This guy is somebody that I think she thought she would find some sort of love with,” the shattered sibling said.

“But he actually took four lives,” Kristen Bachmann said — referring to Juliann and her three children. 

McHenry is accused of stabbing Bachmann in the neck and chest, with the fatal attack taking place in her car and on the ground after he dragged her out of the vehicle, according to a criminal complaint.

The dying woman was rushed to NYU Langone Hospital in critical condition but was later pronounced dead, according to police.

Prosecutors said bystanders dialed 911 during the vicious assault, but the brute took off before police could get to the scene.

McHenry was then picked up by police around 8:15 p.m. Saturday and charged in the shocking, fatal assault, cops said. 

The accused killer was held overnight at Suffolk’s Third Precinct and led to court Sunday, shielding his face from news photographers as he was led out of the stationhouse in shackles with several other prisoners.

He was arraigned in First District Court in Central Islip.

In court, the slain woman’s grieving dad wept as he watched his daughter’s alleged killer — who made faces and glared during the proceeding — be ordered held without bail for the crime.

McKenry, Bachmann’s boyfriend, allegedly dragged her from her car, stabbing her in the neck and chest. John Roca for NY Post

Bachmann was found unresponsive outside a Long Island gas station after the assault. Google Maps

McKenry was paroled in March after serving time for a 2024 second-degree attempted assault conviction. Facebook/Julie Mary

McHenry is now charged with second-degree murder in the brutal slaying of the mom.

Police did not reveal a possible motive and would only say that “the two were known to each other.”

Prosecutors said they were in a relationship.

“I thought we would grow old together,” said Kristen Bachmann, who lives five houses down from her sister, at the vigil. “I really don’t know how to process it all, and I still haven’t.

“She’s going to be looking over each and every one of us, including her babies,” she said of her sister. “She ain’t going nowhere.”

Juliann was part of a tight “trio of besties” with close friends Nay Warren and Tasha Robinson, who helped organize the vigil.

“Today we came together in light and love to remind us that even in loss, the people we love continue to shine bright through our memories,” Warren said. 

McHenry was sentenced to two to four years in state prison in 2024 on a second-degree attempted assault conviction and paroled in March, according to online records.

Additional reporting by John Roca