Well let’s think about it logically, not emotionally. These are the options
1) She was driving home and spontaneously decided she was going to go to her neighbors house and murder him. She gets lucky that his door is not securely closed which helps her gain access to his apartment and she shoots him in cold blood which could potentiality ruin her life for no reason.
2) The spic cop she was fucking said something on the phone that pissed her off. Maybe he said he doesn’t want a relationship with her, just sex. She was distraught and distracted. She was blinded with rage, drove to the wrong floor, saw what she thought was her door propped open, saw someone and in her rage ignored all police protocol and shot him. After shooting him, reality crept in and she realized that she was in the wrong crib and she fucked up.
3). She knew Jean. Maybe she used to sell him weed on the low or some illegal shit. They only had face to face meetings, no phones unless it’s payphones or burners. . He was expecting her so he left his door ajar. Perhaps some deal went bad or he owed her money and refused to pay. She went to his crib in uniform as a means of intimidation but it failed. Maybe he said I’m not paying shit and she flipped and shot him considering she was still blinded with rage over that phone call with her lover.
4) Jean overheard or witnessed something that could cost this cac cop and her lover their jobs and/or freedom. We know from court transcripts that her lover was supposed to meet up with her that day anyway. Maybe the plan was for her to try and intimidate him into not snitching. Maybe they were supposed to go to his apartment together and try to persuade/threaten him to not snitch. For whatever reason his door wasn’t completely closed. I think they said the door used to get stuck a lot and required force to close completely at times... so, a perfect storm... his door is inadvertently left ajar, she goes there and notices the door ajar. She lets herself in without knocking because she feels above the law, especially considering she’s still in uniform. She’s expecting him to be paralyzed with fear upon her arrival where she can have the upper hand, thus having an easier time intimidating him to not snitch. BUT, that doesn’t work.. he immediately jumps up out of his chair and shouts something like get the fuck out of my house while walking towards her. She realizes that after this, there’s no way he will be convinced not to snitch, plus she might have just caught an unlawful entry charge for barging in his house. She hastily tries to save her ass and shoots him dead. Then, of course the whole cover story nonsense.
There’s no other feasible possibility in my mind. I’m curious which one makes the most sense to the people here. Also, if anyone had another probable scenario, add it to my list as #5