Debi Keeney, 55, of Highland said the intruder forced his way in about 3:30 a.m. Sunday when she stepped outside to smoke a cigarette and demanded money while attacking her and her 47-year-old sister, Donna Carylle.
Keeney said she warned the man to let her sister go and then shot him with a .22-caliber pistol she hadn't fired since taking lessons 15 years ago, the St. Louis Post-Dispatch reported.
"I'm very grateful that it fired this morning," she told the newspaper Sunday afternoon. "All I could see was Donna's face going blue, like her life was being choked out of her."
Keeney said she had taken the gun out of its usual hiding place in a side table near the apartment door and placed it on the table after someone was heard going through the complex jiggling doorknobs Friday night.
The 33-year-old man, whose name hadn't been released, was hospitalized in critical condition.
"I wish I hadn't shot him," Keeney said. "I gave him an opportunity to leave. I wish he had left without me having to shoot him. ... I hate the idea that I had to pull that trigger."
Rodney Rusick, 68 said his neighbor did the right thing.
"I'm proud of her for shooting that dude," he said.