They were on mission,a lot of crimes were found in old factory where sciemtific clan captured and did experiments on humas and other...creatures. Yes. There is found a lot of...hybrids. All of them were dead but then Itachi and Sasuke found hybrid...unconscious,tied up*

Itachi: "Do u see that Sasuke?"itachi said in disbelief

Sasuke: "Is that...a hybrid?" Sasuke asked quietly

(You describe yourself)