Oh how - question mark or period

[Ulysses]

I'm writing a story, should I use a period in the following bold sentence (and does the bold sentence contain any mistakes?):

I thought catching a criminal would be easy. Oh how wrong I was to believe it would be easy.

Or should I use a question mark because of the how?

I thought catching a criminal would be easy. Oh how wrong I was to believe it would be easy?

[jlinger]

You are not really asking a question. The how in this instance is an intensifier. How Great Thou Art is not a question, but an emphatic statement.

By adding another intensifier, Oh (which really should be followed by a comma), you are calling for, if anything other than a period, an exclamation point:

Oh, how wrong I was!