What happened to the security force and the missing crew mate?

Just was thinking of this movie today, and for some time I kept wondering what happened with the security team when they came to the station, and also what happened to the crew mate who Snow said just 'disappeared.' So came up with a few questions that I'd like to hear more discussion on!

First off why would the security force start shooting any of the crew? Snow said Kitarn(?) just took off when they arrived so they put a hole in his pot. Don't understand why they just start blasting away at someone running soon as they got there. Past that, the DBA men at the beginning said they lost contact with the security force as it was approaching Solaris, so where did they go? I assume they didn't stick around the station since their ship would still be there but why did they just leave without any communication?

Lastly I'm intrigued by what happened to the crew mate Reese. Again the only mention is by Snow who said Reese just disappeared and they don't know how, all they know is he is no longer on the ship. Does this mean Solaris could have 'pulled' him out for his own alternate reality, or did he die or was killed and just laying undiscovered in some part of the station?

Would love to hear some theories or ideas on these topics, not sure if the old movie or book had any more information on what all happened at the station before Kelvin arrived!