The Dallas Police Department on Friday turned over the case to the Texas Rangers, a law enforcement division within the state public safety unit, citing the need for transparency in the investigation.
In a Sunday night statement, Dallas Mayor Mike Rawlings praised Hall's decision to call in the Rangers "to handle the investigation to ensure there was no appearance of bias."
"Please continue to pray for the family of Botham Jean tonight and in the weeks and months ahead," Rawlings said.
Guyger also shot another man last year, according to court documents.
In May 2017, Guyger was called to assist another officer searching for a suspect. An affidavit indicates a man identified as Uvaldo Perez got out of a car and became combative with Guyger and another officer. A struggle began and Guyger fired her Taser at Perez, who wrested the weapon away from her. Guyger then drew her gun and shot Perez in the abdomen, the affidavit says. Guyger was not charged in the case.
Jean's family has been demanding charges against Guyger in Jean's death. Guyger has been placed on paid administrative leave.