Two women who live on the second floor said they heard shouting before the shots were fired.
The so far unnamed officer (in full uniform) had finished her shift Thursday night when she walked into what she thought was her apartment at the South Side Flats, located about a block away from the Dallas Police Department Headquarters.
Allison Jean in comments Friday broadcast by Dallas TV station KXAS questioned whether the off-duty officer would have reacted differently if she encountered a white man.
Allisa Charles-Findley shared her grief online at the passing of her "baby brother", saying she was just thinking about what to buy him for his 27th birthday later this month.
It was also unclear if the officer was in custody, though Hall said she did not know whereabouts of the officer, whose name has not been released.
Jean, a native of Saint Lucia and a graduate of Harding University in Arkansas, who worked at PricewaterhouseCoopers, a tax and consulting service based in the United Kingdom, according to the Dallas Morning News.
"At the very early stages of this investigation early indications were that we were dealing with an officer-involved shooting". She paused, tears now streaming down her face, before gingerly placing the flowers in front of a sign that read, in thick black letters, "Remember Botham Shem Jean".
At the university, Botham Jean was a "member of Good News Singers, a resident assistant, an intern for the Rock House campus ministry, and a leader in Sub T-16 men's social club", according to the statement. Hall said at the press conference she doesn't know whether the officer knew Jean.
The officer, who was not yet named, will be placed on administrative leave pending the outcome of the investigation.
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Officials added that the officer in question was being tested for drugs and alcohol. When the situation became clearer, Hall made a decision to press charges on the officer.
"We need to push past our initial grief", said Dr. Michael W. Waters, pastor of Joy Tabernacle African Methodist Episcopal Church in Dallas. It's also not clear how she got into the wrong apartment.
The officer said she entered Jean's apartment mistaking it for her own, according to police.
Hall said she hopes the investigation can bring clarity to the family.
"This is a bad tragedy".
This Sept. 21, 2017, photo provided by Harding University shows Botham Jean leading worship at a university presidential reception in Dallas.
"Knowing Botham, I can just imagine him looking into the peephole, seeing the police officer and opening the door because he did no one wrong", his mother Allison Jean told NBC News.
The Dallas County District Attorney's Office is investigating the incident and the Texas Rangers will be conducting an parallel investigation, Hall said.