A teen mom in Oklahoma called 911 to ask if she could kill an intruder before shooting him to death with a 12-gauge shotgun.

Sarah McKinley, 18, killed Justin Martin with a single gunshot wound on New Year's Eve when he kicked in the door of her Blanchard home and came at her with a hunting knife, ABC News affiliate KOCO.com reported. 

McKinley, who lost her husband to lung cancer on Christmas Day, leaving her the sole caregiver to their three-month-old son, first called 911 to request advice.

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

The dispatcher replied: "I can’t tell you that you can do that but you do what you have to do to protect your baby."

Police found Martin, 24, slumped over a floral-print sofa with a single gunshot wound. He was pronounced dead at the scene.

Martin's alleged accomplice, Dustin Stewart, was arrested.

Authorities said the shooting was in self-defense and she will not be charged.

Detective Dan Huff told KOCO-TV that under some circumstances, shooting a person is permissible.

"You’re allowed to shoot an unauthorised person that is in your home," he said. "The law provides you the remedy, and sanctions the use of deadly force."