Joana Cook was at work, about one kilometre away, when the terrorist hit. She could see and hear the emergency response from her office window, which overlooks Westminster Bridge and the U.K. Parliament.

A group of people had been mowed down by a vehicle on the bridge and a police officer had been fatally stabbed at the government building in London.

“As soon as the news alerts started coming in, you could hear all the sirens increasing, helicopters started coming in overhead,” Cook told CTV Saskatoon from the U.K. city on Friday.

Cook, who was born in Regina, has been living in London for close to five years. She’s studying counter-terrorism at King’s College and often visits Parliament for work. She said her first thought when she heard of the attack Wednesday was if those she knows were safe. Then she wondered if more attacks could be coming.

“Is it a single incident? Is this going to be multiple incidents? Just a bit of uncertainty,” Cook said.

The suspect, now identified by authorities as Khalid Masood, plowed a rented SUV into pedestrians on Westminster Bridge then fatally stabbed a policeman inside the gates of Parliament before being shot to death by an officer.

Five people, including Masood, were killed in total.

Cook says, while the attack is tragic, it’s important to acknowledge the response from the community.

“Even on the way home that day, people were thanking police officers for their service. They just lost one of their colleagues there,” she said. “There was a big vigil in Trafalgar Square last night, so we saw thousands of people come out and get together in support of the victims, just in solidarity as Londoners all coming together.”

Muslim groups in the community started crowdfunding campaigns for the victims’ families, she added, saying it’s “encouraging” to see people of all backgrounds stand together in solidarity.

While she felt shock at first, Cook wasn't surprised, as the city had been preparing for an attack and educating people on how to react. She said more than 850 people from the United Kingdom have travelled to Syria and Iraq to join the so-called Islamic State.

“Over half of those have now returned and, while not all of them are dangerous, there is obviously concern that some of them are. There's also an increased risk right now of people being self-radicalized.”

Cook noted it’s important not to let the attack interrupt everyday life or plans for those wanting to travel to the U.K. She echoed U.K. Prime Minister Theresa May’s message that returning to normal is the best answer to terrorism.

Several people have since been arrested as part of the police investigation into the attack. Six people were released without charge Friday night in London, with four remaining in custody on suspicion of preparing terrorist acts.

--- with files from The Associated Press