A white police officer who shot and killed a black man in his Texas flat after apparently thinking she was in her own apartment has been charged.
Officer Amber Guyger is accused of manslaughter.
The family of the victim, 26-year-old Botham Shem Jean had demanded the officer be arrested. Protests were held outside the police HQ over the weekend.
Tributes have been paid to Mr Jean, who worked for the professional services giant PricewaterhouseCoopers.
Officer Guyger has been in the police department for four years and is assigned to the Southeast Patrol Division.
She was booked at the Kaufman County Jail, the Texas Department of Public Safety said. She then posted $300,000 (£232,000) bail, ABC reported, and has been released.
The victim's family have hired lawyer Benjamin Crump, who represented Trayvon Martin and Michael Brown, unarmed black teenagers who were shot dead by a neighbourhood watch volunteer and a police officer respectively.
Mr Crump told a news conference on Monday: "Black people in America have been killed by police in some of the most unbelievable manners.
"You know, driving while black in our cars, black people have been killed walking while black in our neighbourhoods, and now here we are being killed living while black in our apartments."
He was joined at the news conference by the prime minister of the Caribbean island nation of St Lucia, where Mr Jean is a citizen.
Allen Chastanet appeared to fight back tears as he spoke of his anger that a young man could be shot dead in his own apartment.
The Dallas shooting occurred at an upmarket apartment complex just one block from the police department, south of the city centre.
According to a police statement, the officer, still in uniform after her shift, walked into the unit she believed belonged to her and saw Botham Shem Jean inside.
What happened next is unclear, but the officer eventually fired her gun.
She then called for assistance and the victim was taken to hospital where he later died.
An unnamed law enforcement official told the Dallas Morning News that the lights in the flat were off when Officer Guyger fired two shots at a figure moving in the darkness, fatally striking Mr Jean.
The official said that she had just ended a 15-hour shift, when she parked in the wrong garage before making the tragic error.
She was able to enter the flat, because Mr Jean's door was unlocked, the source said, adding that she did not notice Mr Jean's bright red door mat outside.
Officer Guyger was tested for drugs and alcohol at the scene, but the results have yet to be announced.
Video taken by a neighbour shows the officer pacing, and crying into her mobile phone after the shooting.
In a 911 call made by the officer, she can be heard repeatedly telling Mr Jean that she is sorry, local media report.
'A model citizen'
Botham Shem Jean graduated from a university in Arkansas.
He was a devout Christian and an active member of a local church.
Dallas Mayor Mike Rawlings called Mr Jean "a model citizen" and promised a transparent investigation.
The victim's mother, Allison Jean, last week told NBC 5: "Whoever did it to him needs to pay. A heavy price."
PricewaterhouseCoopers said: "This is a terrible tragedy. Botham Jean was a member of the PwC family in our Dallas office and we are simply heartbroken to hear of his death."