DALLAS (AP):

The case against a white Dallas police officer who shot and killed a black neighbour in the neighbour's home will be presented to a grand jury, which could decide on more serious charges than manslaughter, the district attorney overseeing the case said on Monday.

Dallas County District Attorney Faith Johnson said that her office would first collect evidence surrounding Thursday's fatal shooting by officer Amber Guyger, who told authorities that she had mistaken the neighbour's apartment for her own.

The officer was arrested on Sunday night and booked into jail in neighbouring Kaufman County before being released on bond.

Lawyers for the victim's family questioned why it took three days for Guyger to be charged. One said that the officer should have been in handcuffs the night of the shooting, instead of three days later. They also wondered why, based on news reports, Guyger was so quick to use deadly force against 26-year-old Botham Jean.

When asked why Guyger was allowed to surrender somewhere other than Dallas County's jail, Johnson said that the decision was made by the Texas Rangers, who are also investigating.

Citing a law enforcement official who it did not identify, The Dallas Morning News reported that Guyger had just ended a 15-hour shift when she returned in uniform to the South Side Flats apartment complex where both she and Jean lived.

She parked on the fourth floor, instead of the third, where she lived. When she put her key in the unlocked apartment door, it opened. Inside, the lights were off. Then she saw a figure in the darkness, the newspaper reported.

The officer concluded that her apartment was being burglarised, drew her weapon and fired twice. When she turned on the lights, she realised she was in the wrong unit, according to the paper.

Mayor Mike Rawlings also said on Monday that Guyger had parked on the wrong floor.

The Dallas County medical examiner's office said that Jean died of a gunshot wound to the chest. His death was ruled a homicide.

Jean's mother said that investigators had not given her family an account of what happened. Allison Jean told a news conference that she asked many questions but was told there were no answers yet.

The family hired attorney Benjamin Crump, who is best known for representing the families of Trayvon Martin and Michael Brown.

"Black people in America have been killed by police in some of the most unbelievable manners," Crump said on Monday, citing "driving while black in our cars" and "walking while black in our neighbourhoods".

Now, he said, "we are being killed living while black when we are in our apartments".