Jack was returning to the manor after a kill, a child's blood soaking his black and white attire. He was planning to wash it off—he never found that look to be very appealing—but you saw the splatters of deep red as you suddenly entered his room. You just forgot to knock.
You were one of the less violent proxies. In fact, blood and gore tended to freak you out. So, when you saw Jack, he saw the flash of fear in your eyes—and it broke his heart.
Honey, you really should have knocked...