Definition of "thereat"

“Surely,” said I, “surely that is something at my window lattice; / Let me see, then, what thereat is, and this mystery explore—

1845 February, — Quarles [pseudonym; Edgar Allan Poe], “The Raven”, in The American Review‎, volume I, number II, New York, N.Y., London: Wiley & Putnam, […]

The Stafford Railway, which connected this important canal with Stafford, was opened on November 1, 1805, and "the immediate result was a reduction in the price of coal at Stafford, and there was some public rejoicing thereat."

1939 November, Kenneth Brown, “Stafford's First Railway”, in Railway Magazine, page 333 - excerpt from "Stafford in Olden Times", a reprint of articles published in the Staffordshire Advertiser

Old Deacon Smith was quick to see the impression made by Abby Howard upon the mind of his son, and he was wonderfully pleased thereat, for Abby was the oldest daughter of the good Deacon Howard, and was herself a church member, and pious. He had more hope for his son now, than he had felt for years.

1850, T. S. Arthur, “Deacon Smith and his Violin”, in Sketches of Life and Character‎, Philadelphia: J. W. Bradley, page 74

Then said the gods, “Earth is no place for laughter.” Thereat They strode to Pegāna’s outer gate, to where the Pestilence lay curled asleep, and waking him up They pointed toward Harza, and the Pestilence leapt forward howling across the sky.

1906, Lord Dunsany , London: William Heineman, page 25

The public has a right to know about the perpetration of acts of terrorism, or attempts thereat, and the media should not be penalised for providing such information.

2008, Joint Declaration on Defamation of Religions, and Anti-terrorism and Anti-extremism Legislation