Is my Facebook friend lying?

[Marco]

One of my friends on Facebook started a chat with me, saying they were a friend of my Facebook friend. They have done that a few times, to me and other people, often saying weird things that they assume we already know, but is the first time we hear about it, usually quite negative things. In real life, my friend has said some things that I thought were lies, and I suspect that the friend is really them messing around. Do you think they're lying or who they say they are.
My Facebook friend goes to my school so I know them.

[Saphira]

I would delete and block them and also report for harassment. If you dont know who they are you shouldn't add them anyway(unless your a band or something of that nature) People can track you through facebook.

[Vivek]

ya sure,you should block them,otherwise u can be in risk in future

[Hello]

Block them

[Daniel]

Quite Possible i Would Ask your Friend About it Outside of Facebook