Jane Onyanga-Omara, and Kim Hjelmgaard

USA TODAY

LONDON — Some were tourists. Some walked the familiar Westminster Bridge to go to work or school.

After Wednesday, they were united in tragedy: They were among those killed or injured in a terrorist attack in London that left four innocent people dead and at least 50 injured.

Here's what we know about the victims who died:

Keith Palmer, police officer

Palmer (pictured), 48, a father and husband, had 15 years of service on the force. He died from stab wounds sustained while patrolling outside Parliament as part of the Diplomatic Protection Command.

Palmer was not armed when he was killed.

"He was someone who left for work today expecting to return home at the end of his shift, and he had every right to expect that would happen," Mark Rowley, the acting deputy police commissioner of the Metropolitan Police, said in a statement.

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James Cleverly, a British parliamentarian, said on Twitter that he served with Palmer in the Royal Artillery, an army regiment, before he joined the police. Cleverly described Palmer as a "lovely man, a friend."

London Mayor Sadiq Khan also paid tribute to the British police constable. "Keith Palmer was killed while bravely doing his duty — protecting our city and the heart of our democracy from those who want to destroy our way of life."

Aysha Frade, school teacher

Frade, 43, died of her injuries after being struck by the attacker's car when it plowed into Westminster Bridge. She was on her way to pick up her children, 8 and 11, from school. Frade taught Spanish at DLD College London, which is close to Britain's Parliament.

"She will be deeply missed by all of us," the head of DLD College told British media. "She was highly regarded and loved by our students and by her colleagues."

In the northwestern Spanish town of Betanzos, where her mother was born and her two sisters run an English-language school, the mayor said: "The whole town is shocked."

Although Frade was born and lived in London, she spent weeks every summer in Betanzos visiting relatives, said Ramon Garcia Vazquez, mayor of the town of 13,000 in Spain's Galicia region.

He told The Associated Press that her family "was very well known in the village and loved by everybody here."

He said her two elder sisters, Silvia and Michelle, flew to London early Thursday. The Betanzos town hall held a minute of silence for the family at noon Thursday and the mayor announced three days of mourning.

Kurt Cochran, American tourist

Cochran, 54, was visiting London from Utah. He was celebrating his 25th wedding anniversary with his wife, Melissa, who was seriously injured in the attack. They were on the last leg of a European tour.

"Our family is heartbroken to learn of the death of our brother — and son-in-law — Kurt W. Cochran. Kurt was a good man and a loving husband to our sister and daughter, Melissa," his family said in a statement.

Kurt Cochran's wife suffered a broken leg, a broken rib and cuts and bruises, said friend Mike Murphy.

The couple had been visiting Melissa's parents, who are serving as Mormon missionaries in the British capital, a church spokesman said.

The couple ran a recording studio in the basement of their home just outside Salt Lake City.

Murphy, owner of Murphy's Guitars, said Kurt Cochran regularly came to his shop to buy recording equipment for the studio where he tried to help young bands get started by charging them very little.

"He loved music," Murphy said. "He was always around when there were music things going on."

Pictures on Kurt Cochran's Facebook page show the couple enjoying their trip through Europe prior to the attack. In one post, he was smiling and holding a German beer under the caption, "After a long day of sightseeing."

"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," the family said.

Leslie Rhodes

Police said that Rhodes, 75, died after his life support was withdrawn. He was hit by the attacker's car when it hit the bridge.

Rhodes was from Streatham, in south London.

The injured

Police said that of the 50 people injured, 31 required hospitalization and two are in critical condition. One person has life-threatening injuries.

They are a mix of nationalities including three French high school students, all boys, who were visiting London from Brittany. The students were injured on Westminster Bridge when the assailant mowed down pedestrians with a car.

Five South Koreans were also injured in the attack when they were caught up in a stampede of people trying to flee the attack, South Korea's foreign ministry said.

Chinese, Romanian, Irish, German and Polish nationals were also hurt.

Contributing: Associated Press. Hjelmgaard reported from Berlin.