Susan Porter and a colleague trapped Stone in the doors
The security guard who stopped Michael Stone from getting into Stormont has said she feared he was a "human bomb".
Susan Porter told Belfast Crown Court how she trapped him in the revolving doors at the entrance to Stormont.
She said she felt "something hard" around his stomach, and said: "I thought he was a human bomb."
The loyalist killer has said his 2006 storming of the assembly was performance art and denies attempted murder and other charges.
When he was searched it transpired he was wearing a bullet-proof flak jacket.
Stone, 53, denies attempting to murder Gerry Adams and Martin McGuinness as well as 12 other charges of possessing nail and pipe bombs with intent, possessing three knives, an axe and a garotte and having an imitation firearm with intent to commit an offence.
Ms Porter, who has received plaudits and awards for her bravery in tackling Stone, told the court that when she first saw him approaching the doors, she thought he was "frail" and went to give him a hand with his baggage.
However, she said she recognised him and moved to stop the door to ask him what he was doing at Stormont.
She said Stone put a gun to her face and dropped a bag to the floor lighting a fuse and kicking it towards the X-ray machine.
Ms Porter said she "leapt forwards towards the gun" and began struggled with Stone to get it off him, scratching him with her fingernails in the process as he shouted various remarks about "Sinn Fein and Paisley".
Assisted by her colleague Peter Lachanudis, the gun was eventually wrestled from Stone and Ms Porter said as soon as she had hold of it, she realised it was an imitation firearm.
She said that she tried to knee him in the groin then hit him on the hand with the gun, but hit him on the head with it.
She said she was asking Stone what was in the bag only to be told there was "everything, grenades - it's going to go up, get out of here".
She said when she told him he would be blown up as well, Stone replied: "So be it."
As the detained Stone was moved outside Stormont, Ms Porter said she sat on his legs while colleagues searched him, taking two knives and what appeared to her to be "flares" with attached fuses from inside his jacket.
The trial continues.