@Woowon First, we were shown a flashback and based on Jamie's words, it becomes obvious that TJ got the scar while protecting Ian. Secondly, this was just an example of a case that describes well how much Ian is dear to TJ. Thirdly, stop pretending that TJ is the main evil of the plot and Ian is a defenseless fragile boy who cannot stand up for himself. Or when TJ helped Ian overcome drug addiction, did he also ruin his life?