Emma Johnson was collecting her daughter, 15, and son, 17, from the Ariana Grande concert at the Manchester Arena when the lone attacker detonated a nail bomb.
His evil attack killed 22 people and injured 59 – including a little girl aged just 8.
But the mum believes she saw the terrorist among a sea of teens dressed in Ariana Grande merchandise – picking up due to his “intense” red top.
“Then I saw the torso. The remains of a body left as well. It was horrendous.””
Ms Johnson said her eyes were drawn to the man she believes was a terrorist due to “risen” bits on his clothes.
After she noticed him, moments later the arena was rocked by a blast in the foyer.
Armed cops swept on the seen and uncovered the horrific bloodbath – the worst terrorist attack for more than a decade.
She told BBC Radio 5 Live: “I was about 15 feet away from the blast. We were waiting for our children to come out and we stood at the top of the foyer”
She added: “For one split second I turned and saw what I can only describe as a bright red – that’s why it stood out – bright red, with a grey panel down the front with risen bits all over it.
“It was that that stood out because it was so intense, the colour, in this crowd of people.
“As quick as I saw it the explosion happened.”
Police activity in Wilbraham Road, Chorlton, Manchester, following an arrest
The shocked mum described the terrible scene after the blast ripped through the foyer as she looked out for her children.
“It was so loud – then you saw this flash of light and there was smoke and shrapnel everywhere. The glass exploded, people screaming.”
She added: “There were dead bodies everywhere. Then I saw the torso. The remains of a body left as well. It was horrendous.”
Police Respond To An Incident At Manchester Arena
Prime Minister Theresa May revealed the attacker was known to the authorities – and the said MI5 known who he is.
Manchester is in mourning after the horrific attack, which has been claimed by evil jihadi cult ISIS.
Footage showed frantic fans pouring over the railings as they attempted to flee the venue.