I, a personal pronoun, first person singular, masculine or feminine gender, nominative case, subject of the verb see.
now, an adverb of time modifying the verb see.
see, an irregular, transitive verb, indicative mood, present tense, first person singular to agree with its nominative or subject I.
the, the definite article particularizing the noun man.
old, an adjective, positive degree, qualifying the noun man.
man, a common noun, 3rd person singular, masculine gender, objective case governed by the transitive verb see.
coming, the present or imperfect participle of the verb "to come" referring to the noun man.
but, a conjunction.
alas, an interjection, expressing pity or sorrow.
he, a personal pronoun, 3rd person singular, masculine gender, nominative case, subject of verb has walked.