A British astrophysicist was killed when a stray bullet travelled through nearby woodland and a flat wall to hit him as he lay in bed.
Dr Matthew Willson, 31, from Chertsey, Surrey, had been woken by the sound of "rapid gunfire" as he slept alongside his girlfriend Katherine Shephard at an apartment complex in Brookhaven, Atlanta, at 2am on Sunday.
He was then struck by a bullet and later died from a single gunshot wound to the head.
Today police said the shooting is believed to have been a random act, with the bullet travelling less than 100 yards and entering through an exterior wall of the flat.
Sgt Jake Kissel, from the Brookhaven Police Department, said Dr Willson's death is still being treated as a homicide. There have been no arrests so far.
He said: "The two apartment complexes where the gunfire took place and where Matthew was staying, they're separated by a patch of woods, so they back up to each other.
"We're saying it's the reckless discharge of firearms from one apartment complex and the stray bullet travelled through the woods and entered his apartment."
Sgt Kissel noted that investigators are following up on all leads, adding: "We're receiving tips from the public and our investigator team has been working around the clock to ensure that we're tracking down the individuals that are responsible."
Dr Willson had been visiting his girlfriend in the US and the shooting took place three days after he arrived.
A new photo shows the pair relaxing together on the bed with a cat just two days after they were reunited.
Sgt Kissel said: "It's the first of its kind in my knowledge to the city of Brookhaven where an innocent bystander is struck and killed by a stray bullet.
"For me and my 15-year law enforcement career, this is the first time that I've ever dealt with this type of situation.
"It's definitely something that's alarming. It's a tragic event. It's very shocking to hear and try and piece together how it actually happened. It's something that's been... it's a very tall task."
He added: "Our investigation team is treating it as a homicide, even though we believe that it was a random act and complete reckless discharging of firearms, we're still approaching it as a homicide.
"I think that's the best way for us to approach it because that's what we're used to and we're capable of tracking down and viewing the evidence and making sure that we're getting all of those steps and the puzzle pieces put back together, so we are approaching it as a homicide until the evidence dictates something different."
Police were called out to the area over reports of gunshots before they received another call saying a person had been shot.
Officers at the scene assisted with Dr Willson's aid until paramedics arrived, but he later succumbed to his injuries at a nearby trauma centre.
He had been due to stay in the US with his girlfriend for three months.
Ms Shepard told WSB-TV: "He was supposed to be here for three months because we've been long distance for a while.
"I picked him up from the airport, took him to his favourite eating location, and the next day, he's gone."
A spokesperson for the Foreign Office said: "We are supporting the family of a British man following his death in the USA, and are in contact with US authorities."
