HIROSHIMA — Shigeaki Mori, an 88-year-old Hiroshima atomic bombing survivor and historian who confirmed the deaths of 12 American prisoners of war, died at a Hiroshima hospital. Mori researched U.S. and Japanese official documents and tracked down 12 American prisoners of war killed by the Hiroshima atomic bomb.

His research led to U.S. confirmation that 12 captured American service members died in the Hiroshima bombing. He wrote letters to the bereaved families of the 12 American prisoners of war in the U.S. who had not known how their loved ones had died. Mori worked as a full-time company employee while conducting research on American prisoners of war killed in the bombing.

Mori authored a book titled "The Secret of the American POWs Killed by the Atomic Bomb" which was first published in Japanese in 2008. The book won the Kikuchi Kan Prize and was later translated into English.

Barack Obama became the first U.S. president to visit Hiroshima's Peace Memorial Park in 2016. In his 2016 speech at Hiroshima's Peace Memorial Park, Obama mentioned "a dozen Americans held prisoner" among the bombing's victims. Obama hugged Mori during his 2016 visit to Hiroshima's Peace Memorial Park.

"The president gestured as if he was going to give me a hug, so we hugged," Mori told reporters afterwards. "The research I spent more than 40 years was not about people from the enemy country. It was about human beings," Mori later said.

Mori was born in 1937 and was 8 years old when he survived the U.S. atomic bombing of Hiroshima on August 6, 1945. He was approximately 2.5 kilometers (1.5 miles) from the blast when the bomb was dropped.

"I crawled up out of the water and saw a woman tottering toward me. Blood was everywhere on her body, and internal organs hung from her abdomen," Mori told Agence France-Presse before meeting Barack Obama at the Hiroshima Peace Memorial Park in 2016.

"While holding them, she asked me where she could find a hospital. Crying, I ran away, leaving her alone," Mori told Agence France-Presse.

"People who were still alive were collapsed all around me. I escaped by stamping on their faces and heads," Mori told Agence France-Presse.

"I heard screams from a broken down house. But I ran away as I was still a child with no power to help," Mori told Agence France-Presse.

The U.S. atomic bombing of Hiroshima instantly destroyed the city and killed tens of thousands of people. By the end of 1945, the death toll in Hiroshima was approximately 140,000.