A mom and her teenage daughter were gunned down at their Missouri home by a neighbor who was upset with the noise they were making, according to authorities.

The mom, 38-year-old Jessica Lashly, and her 17-year-old daughter, Jersey Greer, were identified by local media after dying from their gunshot wounds late last month.

Their 73-year-old neighbor, Robert Winkelman, walked down the street to their House Springs home on the night of July 25 and began questioning them, the Jefferson County Sheriff’s Office said in a Facebook post.

“From what we've learned so far, there was some sort of a neighbor dispute between the man that approached and the people that lived at that house. It sounds like it was related to a noise complaint,” Captain Matt Moore with the sheriff's office told KSDK.

Winkelman pulled a gun out during the argument and shot Lashly in the head, according to police. When Jersey rushed to help her mom, Winkelman allegedly shot her in the head too.

Winkelman chased a third person with the gun, but she was not shot.

"The witness that came outside with the daughter after hearing the gunshot and was chased by the gunman. She was able to get herself inside the house and lock the door," Moore said.

Police later found Winkelman outside his home, and when they confronted him, he shot himself in the head.

Lashly and her daughter were taken to the hospital in critical condition. The sheriff’s office announced July 27 that they had died from their injuries.

Winkelman, who was charged with two counts of first-degree murder and two counts of armed criminal action, died at the hospital Sunday after being in critical condition, according to authorities.

Jersey was the twin of Justice Greer, who is now left to grieve the horrific deaths of her mom and sister. Justice said she was at work during the shooting.

"It was always just us three," Justice told KSDK. "It's going to be really hard because that's all I'm used to."

Lashly was a single mom whom Justice remembered as hardworking and supportive.

“I never doubted how good of a mom she was,” she said.

Justice and Jersey were going into their senior year at Northwest High School in Cedar Hill, dreaming of playing lacrosse together in college.

"I don't even know how to live without her. We did everything together,” Justice said.

Like any sibling, there were times that Jersey got on Justice’s nerves — those are some of the moments the teen will miss the most.

"I'm really gonna miss...Jersey would annoy me when she'd come into my room, but I'd do anything for her to do it again," she said. "I'll miss her laugh and her contagious smile. Every time I look in the mirror, I see Jersey."

Justice commended her sister’s bravery in the final moments of her life.

“Jersey's last moments, she was trying to save my mom. It just shows how brave she is, and I hope I can be half as brave as she is,” Justice said.

Jersey and Justice’s high school lacrosse team set up a GoFundMe fundraiser, initially for medical bills, but now also for funeral costs. It has raised more than $55,000.

Jersey and her mom are both organ donors. "They'll save so many people," Justice said.