Chapter one.
story related and can't be missed
*** Spoiler - click to reveal ***Get the medicine from the health cabinet, and use the syringe on the medicine.
get a flagpole from the next room, go to the garage and use the flagpole on the sawblade. after this combine the syringe and pole together and add some duct-tape. now you will have a spear. use this on the bear and the achievement will pop