Cambridge University graduates Jack Merritt, 25, and Saskia Jones, 23, were killed by convicted terrorist Khan at a prisoner rehabilitation event in the City of London on November 29 2019.
Khan was released from prison on licence in December 2018, halfway through a 16-year prison sentence, after he was convicted of terror offences in February 2012.
The 28-year-old, originally from Stoke, was living at flats on Wolverhampton Road, Stafford, before the attack.
Amy Coop had been attending the Learning Together conference to make a film for the organisers.
She was in the Banqueting Hall to get footage of a feedback session when she heard screaming and shouting, and went out on to a landing to see what was happening.
At the inquests into Mr Merritt and Ms Jones’s deaths on Tuesday, Ms Coop told the jury: “There was more screaming and shouting and it very quickly became apparent that something very bad had happened.
“As soon as I stepped out on to the landing it was clear that something was going on.”
She saw Ms Jones lying injured on the stairs, with a man kneeling next to her, trying to give first aid.
“She looked very, very unwell,” Ms Coop said. “She was ashen, grey in the face. Her eyes were open and very glassy and staring straight upwards.”
The film-maker went to look for a first aid kit or something that might help stem the bleeding for anyone who was injured.
As she returned to the landing, she heard more shouting, including “a loud and guttural roar”.
She told the jury: “It was a horrible noise coming from someone. It sounded like the kind of thing you see in a film.”
Khan, 28, who was armed with two knives and wore a fake suicide vest, was tackled by members of the public with a decorative pike, narwhal tusk and fire extinguisher, and then shot dead by police on London Bridge.
Earlier, jurors were shown graphic footage of Khan lying on London Bridge after he had been shot for the first time.
The 28-year-old could be seen rolling around, removing his jacket and gloves, while officers kept members of the public back.
Around eight minutes after he was first shot, he sat up, leading police to shoot him again. Less than two minutes after the second shots, he stopped moving.
The inquest is due to go on for several weeks before a separate inquest is held into Khan’s death.