This already happened the second time, after having noticed in in V1.1 before already shortly before update came out. I think there is a pattern. I was playing with the line-of-sight indicator on since round 2 of the ground engagement. The following sequence of events happened: the alien was standing where the purple blood is visible in the screenshot I shot him with the soldier visible in the middle. The shotgun soldier in the upper right corner shot another alien before goin