Mark Townsend heard reports of a serious incident occurring in the London Bridge area, but the 50-year-old was horrified when he heard the extent of what was happening.
The security and risk manager operates a building five minutes away from London Bridge, where three knifemen ploughed into pedestrians using a van at 10.08pm on Saturday and went on to stab people in Borough Market with 12-inch knives during a frenzied attack.
Mark, formerly of Cayton, said: “I called one of my colleagues to see what was happening and heard shots fired while on the phone.
“Being ex military, I knew straight away what it was and I couldn’t believe it. It was then I realised just how serious it was.
“I just told them to get everyone inside and lock up. My first thoughts were with the staff and making sure they were safe, and thankfully they were all OK.
“My officers spoke of seeing people fleeing the area and their terror.”
The attackers, wearing fake suicide vests, were shot dead by eight officers after police fired 50 bullets upon them.
Eight people were killed and at least 36 people remain in London hospitals, with 18 in a critical care.
Police cordoned off the area and around 30 of Mark’s officers were locked inside the building for a whole 24 hours before it being declared safe to leave.
Mark, who left Scarborough at the age of 19 and spent 10 years serving in the RAF, believes the reaction of the emergency services and the public following the terror attack has been tremendous.
The former George Pindar student, who lives five miles away from London Bridge, said: “There has been the obvious initial shock but people are resolute. There’s a Keep Calm and Carry On kind of philosophy here.
“People have been trying to get on like normal but it is a very sad time.
“We can’t let these people beat us and it’s great how people have pulled together.”
Police have identified the three London Bridge attackers as Khuram Butt, Rachid Redouane and Youssef Zaghba.
Twelve people – seven women and five men – who were arrested at two properties in Barking on Sunday were released without charge on Monday evening, police said.
Mark said: “Reflecting on events, you get worried that it is too close to home.
“You just feel for the people who have been killed or injured as well as their friends and families.
“I was getting a lot of calls and messages from people who knew I worked not too far away but thankfully I am fine.”
It is the second terror attack to strike the capital in three months and comes just two weeks after the Manchester Arena bombing.
Twenty-two people, including children, were killed when Salman Abedi set off a bomb as revellers left an Ariana Grande concert.
Superintendent Dave Hannan of North Yorkshire Police said: “The events are truly devastating and no matter where anyone is in the country, we are all feeling the effects of this horror.
“The threat level remains nationally at severe. There is no intelligence to suggest that there has been any change in the level of threat here in North Yorkshire.
“However, I would like to reassure the public that we will be conducting additional patrols and remain visible to our communities.
“We also continue to ask the public to be vigilant and to report anything that they deem to be suspicious immediately by telling a police officer, by calling 101 or by calling the Anti-
Terrorist Hotline on 0800 789 321. Always call 999 in an emergency or for immediate assistance.”