Before he left on a 10-day training manoeuvre, he called his mum to tell her the engagement ring was almost ready.
It had Grandma's diamonds. And Marine 1st Lieutenant Hugh Conor McDowell designed it himself. He'd propose as soon as he returned, he confided. But he never got the chance.
Conor, 24, had asked Kathleen Isabel Rose Bourque to move across the country only four days after they met for the first time face to face.
That surprised his parents and floored hers.
Kathleen packed a bag - a small carry-on was all she would bring to her new life - in the decisive, cinematic moment of their love story.
They met through Hinge, a dating app, rather than any of the District of Columbia places they'd both been hanging out in for years, missing each other countless times.
She liked that Conor's profile picture was a sweet mother-son shot of him, taken during a ceremony at The Citadel.
"Who does that? Include his mother?" she said.
As soon as they connected, they began texting furiously. Then they started talking on the phone.
"The first call was from 10.30 at night until 6am," Kathleen said.
During those calls, they covered it all, from Conor's childhood on Capitol Hill to his DC high school days.
She learned about the sign language he picked up hanging out with his mom, Susan Flanigan, during some of her 26 years working at Gallaudet University, the French he spoke during his summers in a village in Burgundy, his drumming, his recipe for the perfect blueberry pancake.
Kathleen was restless in her small North Carolina hometown, where she was working at a bakery after graduating from Loyola University in Baltimore with a psychology degree.
She had studied military mental health systems, worked for the ROTC department in college and had family in the Navy. It wasn't a surprise she'd be attracted to a military man.
Conor was about to cross the country to report for duty at Camp Pendleton in San Diego.
From the moment his mum explained the 9/11 attacks to him by building the twin towers out of Lego, Conor said he was going to serve his country as a Marine.
"If we had a choice, the Coast Guard would've been nice," said his father, Michael McDowell, an Irish-born former BBC journalist who had played a part in the Irish peace process.
"But he was always going to be a Marine."
Then, he was a Marine falling in love.
"I'm not going to San Diego without meeting you," Kathleen said he told her.
And he got into his truck and drove south to Salisbury, North Carolina. Her mum let him in when he got there.
Kathleen was wearing her favorite white eyelet sundress, and she saw him at the bottom of the stairs.
He was "wearing a Captain America T-shirt, khaki pants and his favorite brown boots", she said.
"He was just so tall and broad and classically handsome."
"I saw him. And that was just it. I just knew, every fibre in my being told me that was it. He was the one," she said.
He stayed for four days. Mimosas and long walks. They went to the amusement park, and she conquered her lifelong fear of roller coasters. They talked and talked.
They'd both done long-distance relationships before. They both hated them.
"Come with me," he urged. It made no sense. They'd met July 11. It was July 15, and she was supposed to run away with him?
But she did it. She packed that small bag and got into his truck.
They drove across the country, windows down, singing out loud.
"In the middle of the country, I freaked out. What have I done? I told Conor that everyone thinks we're insane," she said.
"And Conor said: 'We both know we're insane. At least we're insane together'."
They got a small apartment in Cardiff-by-the-Sea, adopted two cats and a black lab puppy they named Ruthie, who ran in the California surf with Conor.
Kathleen and Ruthie hated it when Conor went on his training operations. He wasn't on foreign soil or facing enemy gunfire. But she knew those training exercises were dangerous.
Training for war, it turns out, has become deadlier for US forces than actual war.
Starting in 2015, training deaths have been outpacing combat deaths every year. In 2017, the ratio was 4 to 1, according to a report by the House Armed Services Committee.
On May 9, Conor was in the turret of a light armoured reconnaissance vehicle with six other Marines.
As the Pacific's early summer morning haze known as June Gloom settled across the training grounds, visibility was poor. That's what some of the six men with the 1st Light Armored Battalion at Camp Pendleton told Michael McDowell when he visited them to reconstruct what happened that day.
The San Diego rains were intense this spring, and the grasses had grown up to 2m high in some places. The men in the vehicle couldn't see very well, and Conor told them to go down below and look through the reticle gunsights, McDowell said he was told.
Just as the gunner was coming back up to report the vision was no better down there, Conor started shouting, "Rollover! Rollover!" The vehicle lurched.
"Conor saved the gunner in the twin turret on his left, quickly pushing the corporal down into the safety of the heavy armour, but it was too late to save his own life," his father said.
The vehicle flipped over. The six Marines inside were hurt, suffering concussions and bruises. But Conor, the only one outside, was instantly crushed.
"They told me they pulled an American flag out to cover his head and torso. They knew he was gone," McDowell said.
The Marine Corps issued a statement about the occurrence, identifying McDowell and explaining that they are investigating.
"We recognise that military operations are inherently dangerous and we take extreme precautions to ensure the safety and welfare of our Marines," the statement said.
"We will do all we can to comfort the family, friends and colleagues of Lieutenant McDowell."
Conor was the fourth person to die in a rollover during military training this year alone.
McDowell says he wants to know more about what happened that morning and wants to make sure it doesn't happen again. It's all a grieving father can do.
"I want to make sure this is fixed, that he didn't die in vain."
Conor's parents, who now live in Chestertown, Maryland, came to San Diego to help Kathleen pack their place up and see their only child's body.
Kathleen returned to Maryland with them. She is living in his old bedroom, reading his field journals. They were full of references to her.
She and Conor were supposed to be planning their wedding. Instead, this Memorial Day weekend, she will be at his funeral.
She still can't believe he's gone.
"Ten days. He was supposed to be gone for 10 days," she said. "Not forever."