Elizabeth Peterson, 64, known to pals by her maiden name Liz Sutherland, was shot dead at 10.30pm on Saturday night in Birmingham, Alabama.
Police investigating the cold-blooded killing are working on establishing a motive.
Liz had moved into her apartment only two weeks before her death, it was reported.
Witnesses were said to have heard shouting and gunfire in the the 2100 block of 17th Avenue South.
Writing on Facebook, Liz’s older sister Morag Sutherland Donlevy, said: “I read and re-read all the lovely condolences for Elizabeth and I cannot fathom the entire thing.
“My mind wanders to an image that I do not want to see.
“We believe in the hereafter and I know for sure my sister did.
“So, in that respect she is safe in the arms of the angels.
“For me, I am a blank right now.”
Liz had recently separated from husband Edward Peterson, and originally hailed from Port Glasgow.
Friends said she worked at Children’s of Alabama and was studying for a degree in social work.
Morag, 73, described it as a “tragedy” and said the killer was “a maniac”.
Posting a childhood snap online, she wrote: “Morag age 19, Elizabeth age 10.
“Back in the day I took her everywhere with me. I shopped for her, slept with her and listened to her wee tales.
“She loved to dress-up. She would take mammy’s lace curtains off the window to play bride.
“She could put her hands to anything - knit, sew, crafts, make draperies, blinds and even cook.
“That is the life this maniac destroyed.
“I hold tightly to the fact that she is the winner in the end as she is finished with this cruel world. Her soul lives on.
“Rest in Peace wee sis.”