Dozens of people gathered in central London on Monday morning to pay tribute to the victims of a terror attack that unfolded near London Bridge on Friday.

Jack Merritt, 25, of Cottenham, Cambridgeshire, and Saskia Jones, 23, of Stratford-upon-Avon, Warwickshire, were stabbed to death while attending a prisoner rehabilitation conference on Friday afternoon, according to London’s Metropolitan Police Service. Merritt and Jones were both graduates of the University of Cambridge and were involved in the school’s Learning Together program, which had organized the conference.

Flowers and letters have been placed at the scene of the attack near the iconic bridge, with one note reading, “I love you forever. I am so proud of you.”

Merritt’s family described him as a “beautiful, talented boy” who “died doing what he loved, surrounded by people he loved and who loved him.”

“Jack lived his principles; he believed in redemption and rehabilitation, not revenge, and he always took the side of the underdog,” his family said in a statement Sunday. “Jack was an intelligent, thoughtful and empathetic person who was looking forward to building a future with his girlfriend, Leanne, and making a career helping people in the criminal justice system. We know Jack would not want this terrible, isolated incident to be used as a pretext by the government for introducing even more draconian sentences on prisoners, or for detaining people in prison for longer than necessary.”

Jones’s family described her as a “funny, kind, positive influence” with a “wonderful sense of mischievous fun” and “was generous to the point of always wanting to see the best in all people.”

“She was intent on living life to the full and had a wonderful thirst for knowledge, enabling her to be the best she could be,” the family said in a statement Sunday. “Saskia had a great passion for providing invaluable support to victims of criminal injustice, which led her to the point of recently applying for the police graduate recruitment program, wishing to specialize in victim support.”

Three other people were injured in Friday’s attack. Two of them remain hospitalized in stable condition, according to London’s Metropolitan Police Service.

The alleged attacker, who was wearing a fake suicide vest, was shot and killed by authorities at the scene. He has since been identified as 28-year-old Usman Khan, a convicted terrorist who was released from prison in December 2018 and had been living in the Staffordshire area, police said.

Khan allegedly began his attack during the prisoner rehabilitation conference inside Fishmongers’ Hall, near the north end of London Bridge, and then proceeded onto the bridge where he was confronted by authorities.

U.K. Prime Minister Boris Johnson and London Mayor Sadiq Khan were among the many dignitaries who attended Monday’s commemorative service at the Guildhall Yard in London, where the crowd observed a moment of silence. Another vigil was also held on Monday in Cambridge.

“The best way to defeat this hatred is not by turning on one another,” Khan said in his address, “but it’s by focusing on the values that bind us, to take hope from the heroism of ordinary Londoners and our emergency services who ran towards danger, risking their lives to help people they didn’t even know.”