AITAH for leaving my coworker with half of the remaining tasks to do at work and complain to the manager about his behavior and attitude?

basically, i had been on eggshells/uncertain about this certain coworker. although we only see each other once a week for less than an hour, i can't help but feel something is off about him. so today i came into my morning shift (a restaurant), and noticed that i had a couple of things that i needed to make and refill. this said coworker (?M) comes in way too early for his shift and on the schedule he comes around 2PM while i finish my shift around 4 (according to the schedule). and since around that time there are usually no rush hour, that leaves us with less tasks to do, so that gives me the cue to clock out early, and since he comes early for work, it should be fine to share some tasks to each other and work as a team.

as i was doing my work, which was surprisingly quite a bit more work than usual, i had planned on dividing the tasks into two since it was overwhelming for one person to complete. usually, in general, we silently agree to share duties for each server that works up front, so one doesn't get to do anything while the other does all the work, and that's what it happened today.

since our schedules overlap when there's no need for two people around that time, i believe that it's fair to split tasks between both of us. but as soon as this coworker comes in and clock in, he goes straight into his break while i was finishing up some of the tasks. i mean, it's fair for him to have his lunch break before i leave because sometimes, later at night, might get busy and then get no time to eat, but i could recognize his patterns when it comes to his break time. he does not show an ounce of interest or initiative at completing tasks; he just crosses his arms and stand there and observe. today i clearly told him that "we got lots to do today, could you please do this thing and another one thing?", was simple and polite but it seems like he didn't bat an eye nor listened.

when he came back from break, he asked me "why did you not make this?" which an annoyed expression and arms crossed. i was like, we should split tasks among each other, not let one person handle all the duties. what was he planning on doing on the meantime i was there, knowing that there was no need for two people to be there? i've done my part of the job and this dude comes to me, with arms crossed and a nasty look at me, demanding why i didnt do the task that i had shared with him? he does not get paid for standing there and watch the other do everything. i dont understand either why the schedule is set up like that. it's unfair how i spent the entire shift, busy with tasks after tasks and taking people's orders all at the same time, and this dude bluntly telling me why i didnt make this certain task among other ones that i had done. every server has the duty to complete their obligations, whether refilling the drinks or any sauces or other items when it's missing.

so in this case, am i the asshole for leaving my coworker with half of the remaining tasks to do at work? it really feels unfair to me, and his attitude was very rude and nasty. i'm also not a confrontational type of person, i felt my body burn in anger inside and left that place completely in distress and anger. i don't want to let anyone there doing absolutely nothing and still earning as if they're working as hard as anyone else in that establishment.

this is not the first time i've faced something like this with this coworker so i had to speak up to someone. and he is not the only one with an attitude like this; some other cashier was put off the schedule for not doing their job properly, with the same attitude as him. might as well happen to this coworker too. but this is for another day to talk about.