ISIS claimed responsibility Sunday for an attack by three knife-wielding men wearing fake suicide vests who mowed down and stabbed several pedestrians in London. They killed seven people before being shot dead in a barrage of police gunfire.
Saturday night's rampage at a popular nightlife hub around London Bridge was the third deadly terror attack in Britain in less than three months and came only days before a general election.
Countersecurity sources told CBN News there is evidence suggesting the terrorists who carried out the attack might have been planning to strike for months. The trigger may have been an ISIS message posted online Saturday calling on followers to use vehicles, guns and knives to "kill the civilians of the crusaders" during the holy month of Ramadan.
As the makeshift memorials continue to grow, police are moving in and making arrests. So far, 12 people are in custody and more are anticipated in the coming days.
We are hearing firsthand accounts of those who fought back against the terrorists.
"Then I threw, I picked up a chair," witness Gerald Vowls recalled. "I was just throwing it at them trying to get them to chase me so I could get them out into the main road."
Police unleashed 50 rounds, killing the three suspects.
Meanwhile, British Prime Minister Theresa May says "enough is enough" and that the U.K. must take tougher measures against radical extremists.
"We cannot and must not pretend that things can continue as they are. Things need to change," she said.
May noted the attack in London was linked to the recent suicide bombing in Manchester by what she called "the single, evil ideology of Islamist extremism."
In the United States, President Donald Trump again called for his travel ban to be put in place and expressed solidarity with Britain.
"I will do what is necessary to prevent this threat from spreading to our shores and work every single day to prevent the safety and security of our country, our communities and our people," he pledged.
Meanwhile in Manchester, people at a Sunday benefit concert paid homage to the victims of the last attack, vowing to stay strong and carry on.
Justin Bieber encouraged the concert-goers, telling them that "God is good in the midst of evil."
However, that evil is an ongoing danger in Britain.
Authorities there say they have around 3,000 people on their watch list, but there is no way to keep track of them all. They believe more attacks could take place.