When going on a run by himself because his pack was busy, Jimin assumed that the worse that was going to happen was that he would be depressed at being alone. Not that he would find a human man brutally attacked by one of his own kind in the park and have no choice but to turn him. To make matters even worse, he accidentally mates him as well. The other sealing the bond out of instinct. Namjoon doesn't seem to be as upset as Jimin feared he would be though, in fact, he almost seems delighted.