Abbie Harrison-Evans was on the train with her partner Ethan Daniels. She said there was a “male shouting from the front of the train” who was “playing spooky Halloween music on his phone”.
His behaviour was “erratic” and her “first impression was he was suffering from a mental condition”, the court heard.
She sent a Snapchat to Daniels stating “we going to get attacked or what?”.
Harrison-Evans said Williams had a black rucksack on the seat next to him and “kept grabbing it and saying ‘I’m going to do it’.”
“It looked like he was reaching for something inside the black rucksack,” she said.
The court heard Williams said “I’m going to do it, I’m going to do it”, followed by “I cannot do it”, and she had a “feeling he was going to hurt us”.
Daniels said he heard the man state: “I am the baddest, no-one is as bad as me.”
Williams is accused of attempting to murder Raza Aslam, Sachin Balakrishnan, Scott Bletcher, Stephen Crean, Kevin Deely, Jonathan Gjoshe, Scott Green, Michael Paffett, David Presland and Samir Zitouni on the London-bound train between Peterborough and Huntingdon on 1 November.
As well as the attacks in Peterborough, he is accused of attempting to murder a teenager on a Docklands Light Railway train in east London in the early hours of 1 November.
The trial has been told that whether Williams carried out the attacks is not in question, but jurors must consider whether he intended to kill those individuals.
The trial continues.
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