Aaron Dean, 34, was one of several officers who responded to Jefferson's home on Oct. 12 after police were called for a welfare check when a neighbor saw Jefferson's front door open in the middle of the night.
Responding officers searched the perimeter of the house and saw a person standing inside near the window, police had said. When he got to the back window, Dean "perceived a threat" and "drew his weapon and fired one shot, striking the person inside the residence," the Fort Worth Police Department had said in a statement.
Dean hit Jefferson with a single shot that killed her, Fox 4 reported. She was playing with her 8-year-old nephew at the time.
After a Tarrant County grand jury indicted Dean on Friday, an attorney for Jefferson's family, S. Lee Merritt, said they are "relieved" by the news, but "we need to see this through to a vigorous prosecution and appropriate sentencing."
The family is "cautiously optimistic that a conviction and appropriate sentence will come in the near future," Merritt said in a statement. "This is a huge first step in the long road to justice for this family."
Dean was initially placed on administrative leave pending the outcome of an investigation. He resigned Oct. 14 and was later charged with murder. He was released on a $200,000 bail. Dean had been with the department since April 2018.
The department had released bodycam footage of the incident "to provide transparent and relevant information to the public as we are allowed within the confines of the" investigation, it said at the time. Any video taken inside the house could not be distributed due to state law.
The neighbor who called 911 about the open front door told Fox 4 in October that the police officers didn't announce who they were or knock on the door before searching the outside of the house.
"When I made that non-emergency call, I didn’t say it was a burglary. I didn’t say it was people fighting. I didn’t say anything to make them have a gun. All they needed to do is ring the doorbell,” James Smith had said.
“They didn’t park up front, they parked on the side. They sent SRT, which is the special response team. They didn’t have a plainclothes officer to knock on that door,” activist and pastor Kyev Tatum had told Fox 4.
Of the nine officer-involved shootings so far this year in Fort Worth, five targeted African-Americans and six resulted in deaths, according to department data.
Nearly two-thirds of the department’s 1,100 officers are white, just over 20 percent are Hispanic, and about 10 percent are black. The city is about 40 percent white, 35 percent Hispanic and 19 percent black.
The October incident came less than two weeks after a white former Dallas police officer was sentenced to 10 years in prison for shooting and killing her black neighbor inside his own apartment. Amber Guyger said during her trial that she mistook Botham Jean's apartment for her own, which was one floor below Jean's. Guyger, 31, was convicted of murder for Jean's September 2018 death.
Fox News' Frank Miles and The Associated Press contributed to this report.