Do you have health insurance for yourself? I think you might want to do a short course of therapy, you might have situational post traumatic stress. Nothing anyone can say will be as effective as professional help to deal with this.
If that's not possible, there is a very good chance these memories will fade somewhat and diminish in strength and frequency...but a good therapist can make that happen quicker.
In the meantime, keep a close eye on buddy's injuries and begin to think about what you could carry with you on walks (stick, pepper spray), to use in the future if that ever happens again.
So sorry you we're put in this awful position. Buddy sure has a sweet face! Take care.
mom to seraphina blue & the cashman
miss jeni-take-a-ride, rescued 7/07
shangri la's great white caesar, rescued 4/09
hearthside's cinderfella (RIP 4/20/09)
shep von bellefontaine (RIP 6/9/10)
voodoo lily (dsh) & cricket (african grey~RIP 7/13)