It was a shocking episode of clarity amid the mayhem that had descended as Israeli troops boarded her Gaza-bound vessel taking aid – among it Frisbees and footballs donated by Hibs – to mentally ill Palestinian children.
For postal worker Theresa, spending her "holidays" on the Challenger 1 as it joined a flotilla of boats bound for Palestine, there was no question of not doing exactly as she was told.
"Up until then I had been pleading with them to stop beating up my friends, I was telling them they were women, they weren't armed, we were non-violent.
"Instead the soldier put a gun to my head.
"I said to him 'You want to shoot me?', and he replied 'Yes, sit down'," recalled Ms McDermott. "I didn't think it would be wise to put him to the test."
The 43-year-old was with journalists, Gaza activists and observers – among them an 88-year-old American man and a Belgian woman making her way to a Palestinian wedding – on a small passenger vessel accompanying larger aid boats, when they were suddenly raided by Israeli troops last week.
Bloody scenes of violence erupted which resulted in troops opening fire. Nine people were killed in the incident, which sparked international condemnation.
Ms McDermott was arrested and later held in custody for three days before being placed on a flight to Turkey.
Her belongings, including clothes, phone, camera and medicines, have gone missing.
Now home in Leith, she insists that the nightmare episode was still worthwhile and that she is determined to do it all again.
"A lot of my co-workers at the sorting office think I'm off my head, but others understand what I'm doing and see that there is a cause behind it all."
Ms McDermott, who helps run the Free Gaza Scotland movement from the front room of her Pilrig flat, set off from Cyprus with the flotilla of three cargo boats and three passenger vessels two weeks ago. The vessel she was helping to crew, Challenger 1, was mainly carrying female peace activists.
It was the second time she had attempted to deliver aid to the area by sea. Her attempt last June ended when Israelis boarded the vessel, the Spirit of Humanity, and arrested everyone on board.
"We were hopeful that because this was a large flotilla, the Israelis would see it as too big a logistical challenge to stop it," she said. "It turned out we were wrong."
She said Israeli soldiers made contact once, at midnight, before suddenly boarding the vessels next day.
"As they approached, three women on either side of the boat stood on the deck with their arms outstretched," she added. "It was clear that we weren't violent and we weren't armed but they started to fire sound bombs – which are deliberately designed to stun you – and smoke grenades and came on board with Tasers.
"It was chaos. They had rubber bullets that exploded and left luminous paint on our clothes so they could identify us.
"One woman had a hood put over her head and another was blindfolded. I was trying to negotiate with the soldiers to take them off and let them join us when one of the two soldiers lifted this automatic handgun and put it to my head.
"I tried to make eye contact with him – I've been told that if you look someone in the eye, it's much harder for them to shoot you.
"I had my hands out in front of me so he could see I wasn't going to be violent. But I wasn't prepared to put him to the test."
As the passengers on board Challenger 1 attempted to reason with the soldiers, gunshots rang out from the nearby cargo vessel, the Mavi Marmara.
Israelis later claimed soldiers boarding the vessel had been attacked and were forced to resort to using their weapons to defend themselves.
Ms McDermott, wounded passengers and others on board the vessels were later held in Beersheeba Prison before finally being forced on board flights to Turkey. "The way they treated people at the airport was appalling," she added.
The incident, however, has not put her off continuing to make attempts to deliver aid to the region.
"I can't wait for my next holidays – I'll definitely be going back," she added.