An American tourist intrigued by the hat of the police officer standing guard outside the Houses of Parliament in London asked for a photograph with him.
Staci Martin could not have guessed then that the officer who politely obliged her request was PC Keith Palmer, the officer who was killed just hours later on Wednesday (March 22).
Martin, who was visiting her son in London, did not see the attack happen.
She told CNN that she saw the news about the attack when back in her hotel room later in the day, and wondered if the police officer she took a photo with was safe.
"We saw the picture on the news and thought it might be the same officer. We zoomed in on the photo and realised it was Palmer," said Martin, who lives in Florida.
"I want to get this picture to his family and I want people to know what a nice person he was and how fragile life can be."
Palmer, a father of two, was one of four people killed in the attack. He was stabbed to death by the attacker, Khalid Masood, as he attempted to stop the latter from entering the Houses of Parliament. Masood was shot dead by another officer.