I was killed by another player, but could not kill him back

I had an incident in the Free Roam mode.

I saw some other players, but they looked like ghosts to me…their images were transparent.  One of them killed me.

When I sent back to them (they showed as a red dot on the radar map) they were still a ghost and I could not harm them.

What gives?  Can someone tell me what’s going on here?

AuthorZac Turner