ST. CHARLES -- A man was shot and killed in St. Charles Saturday evening, and now a homeowner who claims she fired her weapon in self-defense is facing murder charges.

The homeowner, 31-year-old Karen Reisinger, told police that the suspect, 26-year-old Carlton Eugene Ford, Jr., broke into her home in the 400 block of San Juan Drive around 5:30, and was displaying a handgun.

That's when she says she shot Ford at least twice in self-defense. Ford was taken to a local hospital where he was pronounced dead.

During the investigation, police discovered that Ford and another person had broken into Reisinger's unlocked apartment earlier in the day and demanded money and cocaine. Reisinger told police that Ford pepper sprayed her and her daughter during that robbery, which was not immediately reported to police.

But Joe Burkhart, Reisinger's boyfriend who was also in the home, said the woman was only protecting her family, including her children.

“We was sitting in our house. A man barged in, sprayed us with mace," Joe Burkhart said. "My children were there. He even got one of my kids with mace. He cocked a gun to my head and was asking, ‘Where's my money?’”

Joe Burkhart says the armed man then left the St. Charles apartment with cash and a jar of marijuana only to return a while later and force his way inside again, when the shooting occurred.

According to the probable cause statement, Reisinger admitted to detectives that she was angry with Ford for pepper spraying her daughter and said "he needed to die." He shot him twice; the first shot caused him to fall to the ground, and Reisinger said she knew Ford was no longer a threat when she fired the second shot.

Detectives also say the gun Reisinger used was obtained illegally as payment during an illicit drug transaction.

Reisinger was arrested Sunday morning and is being held at the St. Charles jail.

“She don't know what to think, you know? She's upset,” said Burkhart.

Investigators told 5 On Your Side Saturday night they were looking into whether this case centered around drugs.

Burkhart is awaiting trial on drug-related charges but insists this was not a drug deal-gone bad and is standing by Reisinger.

“We have not committed no crimes, none," he said. "If it was their children in that house they would've protected them, too.”

Sunday morning, Reisinger was arrested on charges of first-degree murder and armed criminal action. She's being held on a $250,000 bond.

Police said there were two children between the ages of four and 10 in the home at the time of the shooting. They are both under the care of another family member at this time.

Anyone with any additional information about this crime is asked to call the St. Charles Police Department at (636) 949-3300 or leave an anonymous tip through St. Charles CrimeStoppers at (636) 949-3333.