Burnley Jr. boarded an MCTS bus on Brown Deer Road and became argumentative after the driver told him about a change in policy related to bus transfers.
The driver, who testified in court this week that she was frightened, eventually called officers on board to remove Burnley Jr. from the bus.
Kraemer and Officer Michael Leeman boarded the bus and talked with Burnley Jr. According to police, Burnley Jr. remained argumentative and refused to comply with instructions from police as he was escorted off the bus.
According to witness testimony, all three people fell to the ground in a scuffle after Leeman tripped Burnley Jr.
Leeman said that Burnley Jr. was resisting handcuffs before Kraemer fired a single round into his back.
Burnley Jr., who took the stand during the trial, maintained that he did not resist arrest and that the struggling occurred because officers were having a hard time getting his arms behind his back.
Kraemer's lawyers have argued she was worried for her safety, as well as Leeman's, when she fired her weapon.
Kraemer told investigators following the shooting that she thought Burnley Jr. might be armed or reaching for Leeman's firearm.
On the witness stand all morning Tuesday was use of force expert Robert C. Willis.
Willis walked jurors through still frames of surveillance video captured on the bus during the struggle.
He testified that at no point during the video does it appear the officers have Burnley Jr. under control.
Willis said he believes Kraemer's use of potentially deadly force was reasonable.
"To me, this is a violent, chaotic event," Willis said.
He said Kraemer's fear that Burnley Jr. might be armed or attempting to disarm Leeman was justified.
"Officers can be disarmed in violent confrontations all the time, especially towards the end of them, when they might be injured, or they're exhausted," Willis said.
Burnley Jr. lost part of a lung due to the shooting. He was never charged in connection with the incident.
A use of force expert for the state who testified last week said Kraemer's decision to shoot Burnley Jr. was not reasonable. He said that was, in part, because she was also carrying a TASER at the time of the shooting.
But Willis testified that, in his opinion, a TASER would not have been effective in subduing Burnley Jr.
"The TASER is not trained as a tool we pull out during a fight," Willis said. "It's something we use to stop a fight before it happens. Or it's something we use after the subject is stabilized and it's safe enough for us to go in and force their hands behind their backing using the (TASER)."
Kraemer is currently on administrative suspension from the Brown Deer Police Department, according to Chief Michael Kass.