An 18-year-old Oklahoma mother shot and killed an intruder on New Year's Eve after a 911 dispatcher told her to "do what you have to do to protect your baby."

Sarah McKinley told ABC News that she was home alone with her 3-month-old baby when two men tried to break in her home. One had a 12-inch hunting knife.

After picking up a 12-guage shotgun and a pistol, McKinley called 911.

"I've got two guns in my hand -- is it okay to shoot him if he comes in this door?" she asked the dispatcher. "I'm here by myself with my infant baby, can I please get a dispatcher out here immediately?"

The voice on the phone explained that if her doors were locked, she could use deadly force against an intruder.

"I can't tell you that you can do that, but you do what you have to do to protect your baby," the dispatcher said.

Shortly after that conversation, McKinley used the one of the weapons to kill Justin Martin after he kicked in the door. A second man, Dustin Stewart, later turned himself in to police.

"You're allowed to shoot an unauthorized person that is in your home," Blanchard police Det. Dan Huff said. "The law provides you the remedy, and sanctions the use of deadly force."

Watch this video from ABC's Good Morning America, broadcast Jan. 4, 2012.

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(H/T: The Huffington Post)