You were in shock. Perfectly natural reaction to seeing something like that.
From Wikipedia:
The symptoms show great variation but typically include an initial state of "daze", with some constriction of the field of consciousness and narrowing of attention, inability to comprehend stimuli, and disorientation.
This state may be quickly followed by either further withdrawal from the surrounding situation (to the extent of a dissociative stupor), or by agitation and overactivity, anxiety, impaired judgement, confusion, detachment, and depression. Autonomic signs of panic anxiety (tachycardia, sweating, flushing) are also commonly present.