Why should adults be more aware of a child/young adults being depressed?

I had a friend who had depression and no one knew until after he committed suicide. It has been about 4 years. If people would have known they could have helped him and he would still be here.

so they can prevent a possible suicide ik i had a friend hang herself at my old school in front of everyone

                                                        water

a colorless, transparent, odorless, tasteless liquid that forms the seas, lakes, rivers, and rain and is the basis of the fluids of living organisms.

                                                        halon  

any of a number of unreactive gaseous compounds of carbon with bromine and other halogens, used in fire extinguishers, but now known to damage the ozone layer.

                                                  dry chemical

extinguishing agent used on class a, class b, and class c fires.

                                                  carbon dioxide

a colorless, odorless gas produced by burning carbon and organic compounds and by respiration. it is naturally present in air (about 0.03 percent) and is absorbed by plants in photosynthesis.