"I literally think I just saved someone's life" - member of public helps diffuse tense police standoff

A member of the public helped to diffuse a tense standoff on Wednesday between a homeless man and an armed police officer in Washington, D.C.

Grace McKinnon was on her way back to work after a meeting when she noticed a white police officer pointing a gun at a homeless black man.

"When I saw this situation taking place, I immediately knew that I had to do something," McKinnon said.

"I got out of the car and turned my video feature on to record," she added.

The video McKinnon filmed shows the police officer telling her to back away as he continues to point the gun at the homeless man.

McKinnon says the police officer also told her the homeless man had a gun.

She says that the man, who she identified as Anthony, told her he only had a knife for his own protection.

Anthony can be heard in the video protesting that he was "just trying to sleep."

McKinnon encourages Anthony to get on the ground as directed by the shouting police officer.

"Just get on the ground. It's not worth dying for," she says.

"They killing us out here. It's not worth dying for," she adds.

McKinnon's words seem to strike a chord with Anthony and he lies down on the ground where he was later placed in handcuffs by police and arrested.

"I literally think I just saved someone's life," McKinnon said of the incident.

"I hope the people that are supposed to protect human lives recognise the injustice that is taking place nationally for young black men and women like Anthony and I who are killed every day," she concluded.

McKinnon is being hailed as a hero by many on social media who have watched the video.

Anthony is a homeless man in his early 20's who sleeps at Union Station in Washington, D.C.

He was interviewed by local media back in March when he said he was made homeless two years ago after his mother died of cancer.