A quote becomes divided or interrupted when explanatory words or dialogue tags appear in the middle of the quote.
Dialogue tags are phrases that identify who is speaking and the manner (or attitude) in which they are speaking:
When the explanatory information or dialogue tag appears in the middle of dialogue, it can be sandwiched by commas, or simply be caught between the end of one spoken statement and the beginning of another by the same speaker.
When the divided quote is only one sentence long, use commas to set off the dialogue tag and do not use a capital letter to begin the second half of the quoted sentence (Unless the first word is a proper noun).
When two sentences in a row quoted from the same source are divided by explanatory words or dialogue tags, use a comma to end the first quoted sentence before the interruption, and period after the interruption. Begin the second quoted sentence with double quotation marks and a capital letter.