These are indeed bed bugs, and they are blood-feeders on humans. Please be cautious in assigning "blame" for their introduction. You might inquire whether anyone in the building has traveled in the last few months, and ask what kind of lodging accomodations they had. "Hostel" as an answer should raise a red flag. In any event, you should schedule an immediate inspection of the premises. A proper inspection will not be pretty. It will be necessarily invasive, and time-consuming (2-4 hours). Should treatment be necessary, it will take a minimum of four visits to insure complete eradication (and might involve disposal of some furniture). I hate to be the bearer of bad news, but this is a pretty serious matter. While bed bugs do not carry diseases, immune response to their bites can vary from no reaction to anaphylactic shock. Furthermore, the insects can keep moving, carried unwittingly to infest another location by people in an already infested abode. Good luck. All parties involved may wish to seek legal representation as well, as the major fallout from bed bug infestations appears to be lawsuits.