The American woman stabbed to death in London was the wife of a university professor from Florida who was hours away from flying home.
Darlene Horton was visiting the capital with husband Richard Wagner, who was teaching summer classes, when she was attacked in Russell Square.
Florida State University said the couple had planned to return to their home in Tallahassee on Thursday.
A knife man selected victims at random in a "spontaneous" rampage in the busy Russell Square shortly after 10.30pm on Wednesday.
Horton was killed at the scene and five other people were injured during the attack - the victims suffered a variety of stab wounds including to their chests, back, stomach and arm.
Sky News have named the 19-year-old Norwegian national of Somali origin - who moved to the UK in 2002 - as Zakaria Bulhan from south London. He remains in police custody.
Florida State University president John Thrasher said: "There are no words to express our heartache over this terrible tragedy.
"We are shocked that such senseless violence has touched our own FSU family and we will do all we can to assist Professor Wagner and his loved ones as well as his friends and colleagues in the psychology department, as they mourn."
Florida governor Rick Scott tweeted: "Extremely saddened to hear about the loss of Darlene Horton in London. Ann and I are praying for her family and loved ones."
A British man who suffered a stab wound to his stomach in the attack remains in hospital in a "serious but stable" condition.
An American man, an Australian man and woman, and an Israeli woman were all discharged from hospital on Thursday after receiving treatment for their injuries.