Help Black shadow figure choking my friend?

I was talking to my friend today and he said he saw a shadowy figure. and when he saw it he said it dissapeared and his eyes started watering and then he couldnt breath for like 10 seconds. And then while we were talking something behind him was breathing. He said he saw a white ghost man walking around his house once. When he was 9 he saw the same black figure reach out to the door and then it dissapereed. He is starting to get terrorized by this thing. Tenshons in his house have rose and I know this demonic thing has lead to this. He said he and his mom are fighting. He saw the black figure a total of 3 times 2 within the past year and the white figure very resently. He saw the black figure that choked him like 2 hours ago! What do i do and what should i do to help! I myself have seen ghosts but none like shadowy black demon things. Please help!