If the company was already out there why would they have sent the colonial marines when they could just go down to the planet and grab a Xenomorph? Or why would they go out of their way to infect a person in hyper sleep and just run off without taking them with them? Like if you're going to go through the trouble of breaching the Sulaco and infecting everyone wouldn't you do what they did in resurrection and captivate them?
Either the queen or a warrior did it