There is no evidence Brainna was a cash mule, whatever that is. Let's stick with the facts.
Shortly after midnight on March 13, 2020, Louisville police entered the apartment of Breonna Taylor and Kenneth Walker using a battering ram to force open the door. The police were investigating two men they believed were selling drugs. The Taylor/Walker home was included in a "no-knock" search warrant, signed by Jefferson County Circuit Judge Mary M. Shaw, reportedly based on representations by police that one of the men used the apartment to receive packages. The New York Times later reported that before the raid, the order had been changed to "knock and announce", meaning that the police were required to identify themselves.
The primary targets of the LMPD investigation were Jamarcus Glover and Adrian Walker, who were suspected of selling controlled substances from a drug house more than 10 miles away. According to a Taylor family attorney, Glover had dated Taylor two years before and continued to have a "passive friendship". The search warrant included Taylor's residence because it was suspected that Glover received packages containing drugs at Taylor's apartment and because a car registered to Taylor had been seen parked on several occasions in front of Glover's house. Specifically, the warrant alleges that in January 2020, Glover left Taylor's apartment with an unknown package, presumed to be drugs, and subsequently went to a known drug apartment with this package soon afterward. This warrant states that this event was verified "through a US Postal Inspector." In May 2020, the U.S. postal inspector in Louisville publicly announced that the collaboration with law enforcement had never actually occurred. The postal office stated they were actually asked to monitor packages going to Taylor's apartment from a different agency, but after doing so, they concluded, "There's [sic] no packages of interest going there." The public revelation put the investigation and especially the warrant into question and resulted in an internal investigation. No drugs were found in Taylor's apartment after the warrant was executed.
Kenneth Walker was under the assumption someone was breaking into his apartment, fired a single shot first, striking an officer, whereupon police returned fire into the apartment with more than 20 rounds. A wrongful death lawsuit filed against the police by the Taylor family's attorney alleges that the officers, who entered Taylor's home "without knocking and without announcing themselves as police officers", opened fire "with a total disregard for the value of human life", but Kenneth Walker said there was knocking at their door and the police account claims the officers did knock and repeatedly announced themselves before forcing entry. A New York Times reporter talked to a dozen neighbors and found that only one of them, who was on the staircase immediately above Taylor's apartment, heard the officers shout "Police!" once. The other neighbors said the first thing they heard were shots. However, Kentucky Attorney General, Daniel Cameron, announced on September 23, 2020 that an independent investigation concluded that the officers both knocked and announced their presence at the apartment. This event was corroborated by an independent witness who was in proximity to Taylor's apartment, apartment 4.
Taylor's family has stated there was no announcement and that Walker and Taylor believed someone was breaking in, causing Walker to act in self-defense. Walker said in his police interrogation that Taylor yelled multiple times, "Who is it?" after hearing a loud bang at the door, but received no answer and that he then armed himself. Walker shot first, striking a police officer in the leg. In response, the officers opened fire with more than 20 rounds, hitting objects in the living room, dining room, kitchen, hallway, bathroom, and both bedrooms. Taylor was struck by five bullets and pronounced dead at the scene. No drugs were found in the apartment. According to anonymous sources who spoke to WAVE3 News, one of the three officers allegedly fired blindly from the exterior of the residence, through a window with closed blinds and curtains; the sources said they do not believe Taylor was struck by any of the bullets fired by the officer who was outside.
More than a month after the shooting, Jamarcus Glover was offered a plea deal if he would state Taylor was part of his drug dealing operations. Prosecutors stated that the inclusion of Taylor was in a draft of the plea, but was later removed. Glover declined the plea.