The 16-year-old died three days later.
A police officer has been charged with murder after shooting Jefferson through a window.
They had been on desk duty since 2016.
Hundreds of officers are being scrutinized for racist and homophobic Facebook posts.
Police said she gained control of the officer's Taser and used it against him.
Until this year, the state had long shielded police records from public view.
Only a handful of people have been arrested — until this week.
His cousin said the shooting “seems like an execution.”
But it has nothing to do with the 2014 killing, for which he was never indicted.
In total, three bullets struck the young black man, whom police said they mistook as an armed shooter.
“He pulled a gun on me, walked up to the car,” the officer told the dispatcher. “I had to shoot.”
Last week, Officer Jason Van Dyke was convicted of second-degree murder with a firearm in the 2014 shooting death of 17-year-old Laquan McDonald.