When writing a regex to handle this, you may want to keep in mind other unique names, such as

Mr. H. L. Mencken (first name is an initial)
Mr. Tim O'Reilly (surname with apostrophe or other puncuation)
Mr. Vincent Van Gogh (last name containing a space)
[download]

also note the last two that have no middle initial/name.

If you need to write a regex to handle all of these situations, I do not envy you. ;)