The passerby was thrown into the chaotic scene on Saturday night after he described seeing a man with blood pouring from a stab wound.
He continued: "As I turned to the right, they were attacking a young lady with blonde hair, stabbing her multiple times.
"I could see the evil in their eyes. They didn't look human and they hated everyone," Gerard added.
He then recalled how he bravely stepped out in front of the terrorists to try and stop them from attacking anyone else.
Gerard Vowls recalled the horror he saw from the horrific attacks
This Morning viewers labelled Gerard as a hero
They didn't look human and they hated everyone
"People were throwing bottles at them and a bit after they ran to The Wheatsheaf and that's when I started throwing bottles and shouted, 'Oi terrorist coward'," Gerard added.
The eyewitness then told Holly he was scared throughout the incident, but he "couldn't leave people to die".
As he described the horror of what he saw, viewers took to Twitter to praise Gerard for his bravery that night which potentially saved many lives.
One posted: "Hearing the stories of the people who help in these horrendous attacks are SO inspiring. The bravery is incredible. #ThisMorning."
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London Bridge terror: Scenes as armed police respond Sun, June 4, 2017
At least two people have died after being after reportedly being struck by a van on London Bridge on Saturday night.
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Armed police responding to the incident at London Bridge
Another added: "#ThisMorning This guy needs to be recognised, he's a hero."
A third tweeted: "He is a true hero! Should be so proud of himself #ThisMorning."