An American man has been named as one of the victims of Wednesday's deadly attack in London,
Kurt Cochran, 54 and from Utah, died in the attack and his wife Melissa was seriously hurt, their family has said.
They were celebrating a 25th wedding anniversary and also visiting Melissa's parents, who work on a Church of Jesus Christ of Latter-day Saints mission.
They were struck when the attacker drove a car over Westminster Bridge, near the Houses of Parliament.
So-called Islamic State has said it was behind the attack, which left four people dead, including the attacker. Eight people have so far been arrested.
President Donald Trump tweeted: "A great American, Kurt Cochran, was killed in the London terror attack. My prayers and condolences are with his family and friends."
In a statement released by the church, Clint Payne, Melissa's brother and Kurt's brother-in-law, said the family was "heartbroken"
"Kurt was a good man and a loving husband to our sister and daughter, Melissa," continued the statement.
"They were in Europe to celebrate their 25th wedding anniversary, and were scheduled to return to the United States on Thursday.
"Melissa also received serious injuries in the attack, and is being cared for in the hospital.
"We express our gratitude to the emergency and medical personnel who have cared for them and ask for your prayers on behalf of Melissa and our family.
"Kurt will be greatly missed, and we ask for privacy as our family mourns and as Melissa recovers from her injuries."
Mr Cochran owned a sound recording studio in Utah called the Onion Street Studio.
His LinkedIn page lists him as an engineer involved in tracking, mixing and editing, and highlights his voluntary involvement in a benefit concert called Until the Violence Stops.
In an interview with a local website in 2014, he says he grew up in Maryland and lived in Texas before moving to Salt Lake City in 1983.
He says he got his first guitar at seven but "didn't have much natural talent". He played in a band for a few years before deciding to build the studio.
A GoFundMe page administered by Mrs Cochran's brother to help cover her expenses, says the couple built the studio business from the ground up over the past decade.
Melissa Cochran's sister, Sara Payne-Mcfarland, wrote on Facebook: "My sister, Melissa, has a broken leg, a broken rib, and a cut on her head.
"While we are glad she survived, our hearts are broken and will never be the same after losing our dear uncle, brother-in-law, father. Kurt, you are a HERO, and we will never forget you."
The other victims of the attack have been named as police officer Keith Palmer and Aysha Frade, who worked at a London college.
The attacker was British-born and known to the police and intelligence services. He has been named as Khalid Masood, 52.
Leaders of countries affected by recent terror attacks, including France and Germany voiced solidarity with the UK after the attack.
Mr Trump also spoke by phone to Theresa May to offer his condolences and to praise the effective response of UK security services.
On Twitter, former President Barack Obama wrote: "My heart goes out to the victims and their families in London. No act of terror can shake the strength and resilience of our British ally."