The mother was charged with second-degree murder.
He killed her following an argument with her mother.
The children were left alone by a family friend who brought the gun into the home.
Just two weeks before her murder, her ex threatened to end her life.
Her death marked the first murder in the city of 2018.
The man believed to be responsible for her disappearance is currently sitting on death row for murder.
The couple began dating after meeting online.