A 95-year-old World War II veteran returning home from a trip to Washington D.C. that honored military personnel collapsed and died Sunday, The San Diego Union-Tribune reported.

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Frank Manchel, who served in the Army as a sergeant, had traveled to Washington for a program sponsored by Honor Flight San Diego, a nonprofit that provides an all-expense trip for veterans. The soldiers visit the World War II Memorial, the Korean War Memorial, the Navy Yard Museum and Arlington National Cemetery.

Doctors were unable to revive Manchel, KNSD reported. Manchel was accompanied on the flight by his two sons and spent time during the weekend with his 93-year-old brother, Jerome Manchel, who met him in Washington, the Union-Tribune reported.

“It was almost instantaneous,” Dave Smith, the founder of Honor Flight San Diego, told the newspaper. “He was laughing, chatting, having a good time — and then he collapsed.”

Shelley Zimmerman, a former San Diego police chief whose father was a World War II veteran, was on the trip as a "guardian" -- a volunteer or family member who accompanies the veterans, the Union-Tribune reported.

“He was 100 percent engaged, proud, humble — as these veterans are,” Zimmerman told the newspaper. “You could just tell how proud they all were of him. It was just wonderful, a loving, loving family.”

“My father’s passing was the ending to the most amazing weekend, surrounded by his newest best friends,” Bruce Manchel said in a statement released Monday. “We thank all of you -- Honor Flight San Diego, American Airlines, San Diego International Airport, friends, and supporters for your concern and for allowing the weekend to be so special for all of us to share together. Frank passed quickly and peacefully and the compassion and respect that that was shown to our family will always be treasured. May he rest in peace as he is now with his other beloved son, Jimmy.”

Honor Flights is a nationwide program that serves 141 hubs around the country.

Six other deaths have occurred during Honor Flights around the country, but this was the first from San Diego, Smith said.

"We know this is a potential situation," Smith told the Union-Tribune. "We want to honor these veterans, but this is one of our worst fears that this might happen. We do everything we can to make sure these veterans are safe."

American Airlines has offered to fly Manchel's remains and any family members to his native Michigan for his service and burial, KNSD reported.