Was I in the legal wrong by turning into Drifting while the bus had only its yellow lights flashing?

Today I passed a stopped school bus. I am a junior license holder, aged 17. The incident transpired as follows. I came upon a school bus at an intersection, the intersection is the meeting of Woodbine Rd. and Drifting Dr., Woodbine has a stop sign and is at an end at this intersection. I came up Drifting and saw the bus, with its four way yellow lights flashing, it then pulled past Woodbine, shifted into reverse and backed into Woodbine. I came to a stop on Drifting, at the intersection, and concluded the bus was turning around, I waited, and did not see the driver activating his red flashers, indicating loading or dropping off of students. So after the bus was stopped for about 4 seconds, I made my right turn onto Woodbine, as I rounded the corner, the driver engaged his red lights. I had come fully level with the bus before he engaged his red lights, he then honked at me and I slowed down, but then continued driving as I had already come level with the bus before the red lights were activated. I pulled into my driveway, the first house on drifting, so I assume the driver will file a report and submit it to the police. My question is simple, was I in the legal wrong by turning into Drifting while the bus had only its yellow lights flashing? Also, was it illegal to proceed past the stopped bus with its red lights flashing, after already coming level with the bus? Would it have been appropriate to simply stop along side of the bus? As I previously mentioned, I was unaware the driver had engaged the lights until I was already level with it, in the opposing lane, moving in the opposite direction. I am not entirely certain, however I did not see the driver engage his red lights until I was already level with, and parallel to, the bus.