A black woman was shot dead in her own bedroom by a white police officer less than four seconds after he saw her. 

Atatiana Jefferson, 28, was looking after her 8-year-old nephew on Friday evening (local time) at a property in Fort Worth, Texas, where she lived with her aunt.

Early on Saturday morning, a neighbour noticed the front door of the house was open and phoned the non-emergency police line to ask officers to check on Jefferson.

At about 2:25am two officers arrived at the scene and walked into the backyard. One officer saw Jefferson through a bedroom window, drew his gun and shouted "put your hands up, show me your hands" without identifying himself as police.

He then fired his weapon, fatally shooting Jefferson. Body camera footage reveals the entire exchange took less than four seconds. A police spokesperson told media Jefferson's nephew was in the room when she was shot.

Jefferson died from her injuries at the scene. 

Police have released a photo of a gun inside the house, which the Jefferson family's attorney has called "reckless and irresponsible" because they did not provide any context. 

"You didn't hear the officer say 'gun, gun, gun'," Lee Merritt told NBC. "He didn't have time to perceive a threat. That's murder."

He says the family believes Jefferson, who spent the last evening of her life playing video games with her nephew, thought the officer was an intruder prowling in her backyard. The unidentified officer, who has been with the Fort Worth Police Department since April 2018, has been placed on leave. 

It's the sixth deadly shooting involving an officer from the department since June, and comes two weeks after a white Dallas officer was sentenced to prison for murder after shooting her black neighbour in his own home. 

Jefferson worked in pharmaceutical equipment sales and intended to study medicine, according to her family.

James Smith, the neighbour who made the non-emergency call to police, told local media he blames himself for Jefferson's death. 

"If I had never dialled the police department, she'd still be alive," he told the Fort Worth Star-Telegram.

"It makes you not want to call the police department. If you don't feel safe with the police department, then who do you feel safe with?"