The findings of the criminal investigation will be presented to Oklahoma County District Attorney David Prater.
The off-duty officers were wearing Oklahoma City police uniforms, Nelson said.
Officers are allowed to work side security jobs in uniform, he said.
Simms did not have a police record in Oklahoma City and had been in town only for a few days.
A request to the Olathe police for any police incident reports involving Simms did not receive an immediate response. A search of Corrections Department records in Oklahoma and Kansas didn't produce any records involving him.
Avery declined to comment about whether her brother had any gang ties or criminal activity.
She remembers him as a goofy person, a lot of fun, with a ton of energy.
She said she found it strange he was carrying a weapon at the time of his death.
“He made friends everywhere he went,” she said. “He was basically a cool and laid-back guy.”
Simms was the oldest of seven siblings, she said.