A 4-year-old boy in Washington State found a loaded gun under a mattress in an apartment on Saturday and shot his pregnant mother in the face, authorities said.

The 27-year-old woman, who is eight months pregnant, was watching TV with her boyfriend when her son found the firearm, King County Sheriff’s Office spokesman Sgt. Ryan Abbott said. The shot was unintentional.

The woman was taken to a hospital with life-threatening injuries. She was transferred to another hospital on Sunday when her condition improved.

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Abbott said the gun was unregistered, the report said. The boy’s father allegedly told authorities he had borrowed the gun for protection. The case is under investigation.

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Under a new state law, gun owners could face criminal charges for not safely storing a gun, but Abbott noted that the law doesn't go into effect until July. The condition of the unborn baby was not reported.

The Associated Press contributed to this report.