Satellite accelerated and changed directions around a seperate satellite very suddenly and quickly.

My Dad and I were relaxing on the front lawn by our house watching the stars and chatting. I saw three satellites come up over the trees from the Northwest, heading East. They were bright white lights like typical satellites, but they were extremely bright (I estimate an apparent magnitude of -3.5).
 I pointed out to my dad that there was a Starlink train coming up over the trees but it stopped at three satellites. A few seconds after they had all cleared the trees, the third satellite in the line suddenly vanished.
 The other two continued on for another five seconds before the second satellite accelerated very quickly to the South. Assuming this was in LEO, they may have been traveling at four or five miles per second. Based on this I estimate the satellite accelerated to upwards of eight miles per second in less than three seconds.
 The satellite then accelerated to nearly twice its original speed as it's still curving towards the south. Once it had finished accelerating towards the East, the satellite immediately began curving back North, stopping its Southward movement and accelerating to the same speed in the opposite direction in only a few seconds.
 Once it was perfectly in line with the other satellite it ceased all movement on the North/South axis immediately as if it had hit an invisible wall. It continued to gain distance between it and the other satellite before it vanished. The remaining satellite continued on as normal.