The red cheater killed Emma (npc). (Dark Souls 3)

Hello everyone. I started anew the passage, already approached the Vordt, did not have time to talk to Emma (azure covenant), as a cheater invaded me. It looked like a homemade purple graphic stain two preachers thick. The sight was not focused on him, the damage did not pass. At first I thought that my video card was overheated. He emerged from the room with Emma, ​​the high priestess. I ran to the fire, waiting for him so that I wouldn't run far for souls. It appeared out of nowhere behind my back, killed me. Do not care, revived, burned coal, went to Vordt. I went to get the azure covenant and talk to Emma, ​​but she's gone. An azure covenant is lying on her chair, a bowl of oaths and it seems that there was something else, I'm not sure. Then the fight with the dancer began, and I flew away to the fire immediately.
And now the question is, how is this possible?