22 people killed and 59 others injured, most of them children.
One of the victims was an eight-year old girl, who'd gone to the Ariana Grande concert in Manchester, with her mother and sister on Monday night.
This is the second attack in the UK that's been claimed by ISIL this year.
Five people were killed on March 22 when British-citizen Khalid Masood drove his car onto the sidewalk along Westminster bridge.
The British government has tightened security and is freeing up nearly 4-thousand soldiers to help police, if needed.
It's also raised its terror alert to the highest level.
But will any of these steps prevent further attacks?
Presenter: Richelle Carey
Rizwaan Sabir - Assistant Professor in Criminology at Liverpool John Moores University
Andreas Krieg - Assistant Professor at the Defence Studies Department at King's College London and a specialist on armed groups
Oz Hassan - Associate Professor at University of Warwick and a specialist on counter-terrorism
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