Hall says the department was readying a warrant for her arrest when rangers intervened, claiming they wanted to speak with Guyger first.
The Texas Rangers are investigating and an attorney for Jean's family has called on the authorities to arrest Guyger.
Guyger was involved in another shooting incident in May 2017, when a suspect took her taser, according to a Dallas Police Department press release. Her initial remarks at a news conference were also posted on the Dallas police blog.
Court documents show that the Dallas police officer involved in the fatal shooting of a black man earlier this week also shot a man during a confrontation in 2017.
The shooting occurred just before 10 p.m. CST at the South Side Flats, an upscale apartment building south of Dallas' downtown.
She says going forward the group expects transparency and accountability in the case.
"On behalf of the Dallas Police Department, we are continuing to pray for Mr. Jean's family, and ask that the community remain patient as this investigation is conducted", said Hall.
He told reporters Saturday that the Texas Rangers, the top criminal investigative agency in the state, has taken over the probe into the shooting death late Thursday of Botham Jean. "We know she (Guyger) used her service weapon. when people saw her in the public, they believed she was a police officer. for us, it enhances the culpability". The department said the investigation is ongoing and that no additional information was available.
On Friday, Dallas Police Chief Renee Hall said that an arrest warrant was forthcoming for Guyger's arrest and added that she would likely be charged with manslaughter.
Guyger, who has been on the police force for four years, called 911 for assistance and Jean was taken to a local hospital where he later died from his injuries, police said.
Officer Amber Guyger was arrested and booked into the Kaufman County Jail Sunday night for the killing of 26-year-old Botham Jean, ABC News Affiliate WFAA reported.
"I don't think there was a student on campus who didn't know Botham", said Landis Tindell, who knew him as a resident adviser.
A lawyer for Jean's family said Saturday after a prayer vigil at a Dallas church that an arrest warrant should be issued for the officer. Guyger pulled her gun and fired twice.
"Botham loved mankind", Jean's mother, Allison said to those gathered.
"We are totally committed to getting to the bottom of this situation", Hall said Saturday while taking questions about the shooting during a leadership summit at Paul Quinn College. Ms Hall said the officer's blood was drawn at the scene so that it could be tested for alcohol and drugs.
Jean was a graduate of Harding University in Arkansas and was said to be an active member at his church, according to reports.
"Super scary because the police are supposed to protect you and then they come home and you're just hanging out in your own house and then they come home thinking they're home or whatever", he said.