I remember one time when I was going it alone, and saw a group of probably 3 people. They were being chased by zombies, and one went down while the others were getting mauled. I moved in, taking a risk, to save this guys life. After bandaging him, I waited to give him morphine to confirm wether or not these guys are friendly. They sounded like they needed to change their diapers, so I trusted when they said yes we are friendly. I continued to treat the one who broke his legs being chased, helped finish off the zombies in the area, and then gave all 3 of them blood transfusions and what medical supplies i had left. as soon as I finished, they shot me. Trusting people is more risky than it seems in this game sometimes :(