Is ipsum/ipsa/ipse a third person pronoun, or can it serve other functions?

The pronoun ipse is not a third person pronoun.

1. What type of pronoun is Ipse?
2. Is ipse a reflexive pronoun?

What type of pronoun is Ipse?

In Latin, the intensive pronoun is ipse, ipsa, ipsum. It applies to all three grammatical persons. In other words, the same pronoun can mean “myself,” “yourself,” “himself,” etc.

Is ipse a reflexive pronoun?

So it is like very intensified "He" in this sentence (a subject to viderat). + ipse is not used reflexively in Latin, it's just an intensifier to demonstrative/semi-personal pronouns as "is, ea, id" (not used together, of course)...