How can I know if my two year old is seeing something I can't see?

Hi there!

I have a two year old. He is generally happy, healthy, and sleeps well enough. He does have a hot, hot temper. Lately, he keeps telling me that someone is coming up to the house outside. Yesterday he said he heard voices and that a skeleton came up to him and scared him. He seems calm about all of this, however.
Months ago, he looked out the window where there was no one and said, "Don't do that!". He said a man was trying to take his art work off of his art easel.
I've responded to him calmly about all of this... just saying, "Is he still here? Are you still scared? Let me know if he comes back."