I feel disllusioned and depressed?

Last term I went walking with my friend at around 11:00 or 12:00 at night we went to buy sodas at home and then were cming back home as we walked past my school. As we passed it there were teenagers trespassing on it and were at the sports hall hving drinkups and blasting music from its speakers. We decided to check it out and while in there, my friend asked 2 guys for weed. they either said they didnt have any or didnt reply. we left the rec hall wandered up to our classrooms and then went back down to the rec hall which was near the field. as we were leaving the hall and getting onto the field, a tall, plump guy 18yold walked up to us with a group of party goers and angry looking teen boys he asked us wethere we knew kristy or something? confused my friend said he didnt knw and the guy punched him in the face. after that my friend shat his pants lterally and i tried to get in front to stop the guy from continuing to punch him, as I did someone punched me in the back. I ignored cos i didnt one to start a fight as I was outnumbered so then when tried to stop, the big guy he punched me in the face. thats when me and my crap dripping friend tried running away. the teens and big guy ripped our valuables off us as we tried to get away and then tackled my mate to the ground, i tripped and fell grazing myself very badly. the big guy and his gang procedded to kick the living daylights out of my friend on the ground while I could do nothing but watch as the guys did not touch me. I moved closer trying to tell them to stop while my mate kept cringing on the ground as they put fists and legs into him. One of them punched me in the head again. I realised i could do nothing so I ran off to the police beat which was only a block away. I didnt knw how to contact the cops however as u had to pick up a payphone or something. I then went to a nearby house and told them to call the police. they promised they would and i was left standing outside their door alone. I did not want to run back up there to my friend as I knew they would be bashing the daylights out of him and I was scared, ok. Then a bystander who was at the illegal party called out from the street and said he had my mates phone and that my mate ran off. I walked with him back up there, he gave me the phone and I saw my mate bleeding and walking up a different way. I went to him and saw he had lost his bag and hes face was worse then mine. he had a bleeding nose, badly grazed and bleeding arms from when they dragged him and a cut eye. We had to get away before those people saw us together so thanking the bystander we ran away from that area and hid at a randoms house until the ambs and police came to get us. as we drove off in the ambs i could here them laughing and talking to themselves. those bastards. My question is this,,, I know I shouldnt have been walking at night there but if I had, what could I have done to prevent them stealing from us and bashing us up? I feel depressed because I was so vulnerable and I feel guilty that I ran away and my mate got bashed more while I only had knee grazes and a bloody nose. I feel guilty and I have lost my pride in the fact that I can protect the ones I love? by the way me and my buddy are 16 yold boys who got bashed in their own school. Please clarify what i could have done to diffuse the situation or if not fight back without fear?? Im so depressed and guilty as well as ashamed right now cos my things were also stolen? :(. sensible indepth ans pls.