The accident
I don't believe that girl - Cheri? - was responsible.
Any place where there is a "Stop" sign would make a driver with even a minimal experience slow down and check the traffic around them. Not to mention that the speed you need to be driving at to kill one person and to cripple another...
Clay's friend might have been sober but he was most definitely speeding and the old guy clearly was distracted. Their fault - not hers.