Salman Abedi, who detonated a suicide bomb in Manchester at an Ariana Grande concert last Monday, bought most of the component bomb parts himself, according to police. BBC reports that most of the planning was “carried out alone” in fewer than four days leading up to the attack, according to the head of the North West counter terrorism unit, Russ Jackson. Police have not ruled out the theory that Abedi was part of a wider network of terrorists when he planned the attack, which killed 22 people and injured dozens of others. So far, 16 people have been arrested in connection with the attack. Five have been released without charge.