A 19-year-old man has been charged with carrying out a knife attack which left an American tourist dead and five other people injured in London's Russell Square.
Zakaria Bulhan, a Norwegian national of Somali origin who moved to the UK in 2002, is due to appear before Westminster Magistrates' Court on Saturday.
Darlene Horton, the 64-year-old wife of a university professor from Florida, was just hours away from flying home when she was killed in the attack on Wednesday evening.
She was visiting London with husband Richard Wagner, who was teaching summer classes, and the couple had planned to return to their home in Tallahassee on Thursday, Florida State University said.
A British man who suffered a stab wound to his stomach in the attack remains in hospital in a "serious but stable" condition while an American man, an Australian man, an Australian woman and an Israeli woman were all discharged from hospital on Thursday after receiving treatment for their injuries.
Yovel Lewkowski, 18, who was visiting London from Tel Aviv was stabbed in the upper arm.
She said she did not know whether to call it "luck or fate" that she escaped death, adding that she had watched as Ms Horton "perished in front of my eyes".
In a moving Facebook post, she wrote: "I'm not afraid, I want to keep going with the trip.
"The last few hours have taught me to appreciate every second, I don't know whether to call it luck or fate, but no doubt it is some sort of miracle compared to the woman who stood right next to me and perished in front of my eyes: a matter of seconds, metres, breaths."
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."
Friends and neighbours expressed shock at the arrest of Bulhan, a former student at Graveney School in Tooting, south London.
Neighbour Parmjit Singh Bhamra described Bulhan as a "quiet, academic boy who was a bit of a loner" who liked football, basketball and music.
He said Bulhan, who is unemployed, lived at the flat with his younger brother Salah, who he thought was about 16, and his elder sister Segal, around 24 and known in English as Hannah, and their mother Safia, whom neighbours call "auntie".
Two police officers remained on duty outside the Bulhan family home on Friday, a council flat in Robertson House on a road adjacent to St George's Hospital in Tooting.