Wang Zhongwen served as Registrar of Henan Prefecture, and resided to the north of Koushi County. He set off to return home in response to an auspicious sign. His route took him through an area of marshes and lakes, where he spotted a white dog following behind him. Zhongwen became very fond of it, and wanted to take it home, but it suddenly transformed and took on human shape. Standing six feet tall, and looking like a Fang Xiang mask,[1] with eyes of red flame, grinding teeth and a wagging tongue, it was quite abhorrent. He wanted to attack it, but it repulsed his assault for a time, and tried to get onto the carriage. Zhongwen was terrified, and quickly ordered his servants to beat it, but they were quite unable to do so. He thus dismounted and lashed out alongside his servants, but still could not hold it back. Their combined strength exhausted, they could strike out at it no longer, so gave up and fled. They told others of this, and, gathering ten or more people, wielding blades and clutching torches, they went together to see it, but were no longer able to find the place. After a month and a day, Zhongwen suddenly saw it again. He and his servant fled, but, before they could reach human habitation, he fell over quite dead.
From Xusoushenji.
Li Fang 李昉, et al., Taiping guangji 太平廣記 (Extensive Gleanings from the Era of Great Harmony), 10 vols (Beijing: Zhonghua shuju, 1961), vii, 319.2532:
王仲文
王仲文為河南郡主簿。居緱氏縣北。得休應歸。道經水澤。見後有一白狗。仲文甚愛之。欲便取。忽變如人。長六尺。狀似方相。目赤如火。磋齒嚼舌。甚有憎惡。欲擊之。或却。或欲上車。仲文大怖。便使奴打。不能奈何。因下車。佐奴共又打。亦不禁。並力盡。不能復打。於是捨走。告人家。合十餘人。持刀捉火。自來視之。便不知所在。月餘日。仲文忽復見之。與奴並走。未到人家。伏地俱死。出續搜神記
[1] This seems likely to refer to a ritual four-eyed mask worn by exorcists heading funeral processions. See https://en.wikipedia.org/wiki/Fangxiangshi, https://dreamingsnowflake2013.tumblr.com/post/151446420249/the-warrior-who-defeats-evil-bangsangshi, http://yokai.com/housoushi/.