Did David Cash do the right thing?

David Cash aka "the bad Samaritan" was a young 18 year old who was in a Casino game room with his friend Jeremy Strohmeyer. They're been there for a while because it was 3:47am, they saw Sherrice Iverson walk into the women's bathroom and they decided to follow into the bathroom. Sherrice Iverson was a young 7 year old African american who's dad was gambling while she played in the game room by herself. Once they were in the bathroom with her, Jeremy was playing around with her, throwing toilet paper at each other. at this time there still hasn't been anyone who was entered the bathroom. Out of nowhere Jeremy takes her into the stall and locks it, then David Cash was curious so he decided to look over the stall, and when he did he saw Jeremy holding her in a sexual way and telling her to shut up or he will kill her. David then just decided to tap him on the head and give him a "look" that indicated that he should stop and leave, but Jeremy ignored it and continued. While this was happening David decided to go for a walk and not report anything to anyone. After 25 minutes, Jeremey walks out of the bathroom and tells Davis that he raped and murdered her. David didn't say anything and they left to Las Vegas to spend more time playing games. I personally believe that the action David did was not ok because he could of stopped his friend and he would have never been in jail nor Sherrice wouldn't have died. How hard was it for him to call the cops? He could of just told his friend to stop not just give a look, if he really cared about his friend he would of told him to get out because he can go to jail for raping her but he decided to let him do it and act like he didn't see shit. What do you think? what would you have done?