Used for emphasis, or when resuming after diversion or interruption.
1912, Clarence Young, The Motor Boys on the Wing: Or, Seeking the Airship Treasure (page 63)
"Stop! Stop I say!" ordered the professor imperiously.
1823, William Wilberforce, Appeal to the Religion, Justice and Humanity of the Inhabitants of the British Empire in Behalf of the Negro Slaves in the West Indies
When such men as Mr. Burke, Mr. Dundas, Mr. Pitt, Mr. Windham, and my Lord Grenville: when such men as these unreservedly and repeatedly avowed their sentiments on the condition of the Slave; when they saw no danger in the avowal; […] when, I say, these men thus thought, spoke, and acted […]