British astrophysicist Matthew Willson arrived in Atlanta, Georgia, on 14 January to visit his girlfriend Katherine Shepard.
Less than two days later the 31-year-old was dead, struck in the head by a stray bullet while lying in bed with his partner of three years.
Police have launched a murder inquiry and are appealing for witnesses to the shooting on Buford Highway in the Brookhaven neighbourhood.
His heartbroken girlfriend, 25, told WSB-TV they had been in a long-distance relationship since meeting at the University of Georgia in 2018, and had been planning to spend the rest of their lives together.
“I picked him up from the airport, took him to his favorite eating location, and the next day, he’s gone.”
How did Matthew Willson die?
Ms Shepard said the couple had been in bed at her apartment in the early hours of Sunday morning when they heard shots going off from a neighbouring apartment complex.
“At first there were just a few gunshots, then there were more and it sounded as if whoever it was had emptied out their clip,” Ms Shepard told The Sun.
“I turned to Matthew and said, ‘I’m going to call the cops’. His last words were, ‘Sure, I’m sure they are just messing around’.”
Ms Shepard had just phoned 911 when she heard the gunfire started again and a small explosion next to the bed.
“I remember a piece of the wall hitting me on the leg,” Ms Shepard told The Sun.
“I turned on the light, looked round and Matthew was slumped in front of me. I could see he had been shot in the head.”
Officers were already in the area responding to the shooting when they were alerted that Mr Willson had been shot.
“I held him for another 20 minutes while we waited for the ambulance,” Ms Shepard told WSB-TV.
“And while we were waiting, there were more gunshots fired. I was just trying to keep him there, you know, talking to him.”
Sergeant Jake Kissel of the Brookhaven criminal investigations division said officers provided medical aid at the scene until paramedics arrived. Mr Willson was raced to hospital where he later succumbed to his injuries.
The shooting appeared to be a “random act involving individuals participating in the reckless discharge” of firearms, he said.
Police are offering a cash reward for information that lead to an arrest.
Ms Willson’s sister Kate Easingwood, who travelled from her home in Sweden to Georgia, posted a photo of her brother to Instagram with the caption: “This world is so unfair.”
“I don’t come from a country that has gun culture or any kind of gun crime like this,” Ms Easingwood told the local news station.
“It’s even more shocking for me that my innocent brother was caught in the crossfire.”
A UK Foreign Office spokesman said: “We are supporting the family of a British man following his death in the USA, and are in contact with US authorities.”
An accomplished academic
Mr Willson, from Chertsey, Surrey, was an accomplished researcher whose academic pursuits had taken him all over the world, family said.
He worked as a postdoctoral researcher for two years at the University of Georgia’s Physics and Astronomy Department, where he met Ms Shepard, a fellow astrophysicist, in 2018.
He graduated with a PhD from the University of Exeter in southwest England where he was a “much-loved member of our astrophysics team,” a university spokesman said in a statement.
“Our hearts go out to his family, friends and colleagues. We are offering support to colleagues at the university who will also want to commemorate his life,” the university spokesman said.
Mr Willson also worked at the University of Liège in Belgium, The Evening Standard reported.
Mr Willson co-authored several academic papers that were published in The Astrophysical Journal Letters.
His research areas included the origins of stars and planet formation.
“As the number of known exoplanetary systems has grown, it has become increasing apparent that our current understanding of planet formation is insufficient to explain the broad but distinct distributions of planets and planetary systems we observe,” Mr Willson wrote in his doctoral thesis for University of Exeter in 2017.
According to NASA, the three broad questions astrophysics seeks to answer is “how does he universe work, how did we get here, and are we alone?”
Space.com describes astrophysics as a branch of space science that applies the laws of physics and chemistry to “seek to understand the universe and our place in it”.
It explores topics such as the birth, life and death of stars, planets, and other celestial objects in the universe.