Discussion

While it seems like “shedding crocodile tears”, this idiom refers to true sadness: the death of a hare refers to sense of unease and deep sadness (based on a classical allusion where hares and foxes share a common enemy: hunters). Although the meaning is somewhat subtle, this idiom is reasonably common and well worth learning:

兔死狐悲 tù sǐ hú bēi / tuh syy hwu bei “[literally] When the hare dies, the fox grieves = sadness at knowing that someone in a position similar to yours (not necessarily a friend) has gravely suffered, mixed with worry that your time will also soon be up.

[title image is PD photo from Pixabay]

Side Note

Eagles mostly feed on fish, but they occasionally steal prey from other animals. On the other hand, foxes are opportunistic omnivores: they eat whatever they can find, sometimes with quite surprising results:

兔死狐悲 Sample Sentence 1

This first quote refers to the dismay experienced by a woman who had grown used to chatting and interacting with a female coworker who inexplicably disappeared one day after giving the standard excuse (in Chinese offices) that she had to take care of some family problem.

[full text of the original quotation: 兔死狐悲的凄凉 http://blog.sina.com.cn/s/blog_5d6a02290101ft3z.html]

兔死狐悲 Sample Sentence 2

This second quote alludes to the fact that some rich Chinese who drive up the price of real estate in many prosperous countries seem to be outlaws wanted by the PRC government. In this particular context, 兔死狐悲 seems somewhat similar to “the writing is on the wall”, a warning that disaster is coming.

[full text of the original quotation: 中国逃犯怕了：李东哲兄弟高山夫妻兔死狐悲http://m.creaders.net/news/page/479410]

The English idiom "The writing on the wall" based on an incident described in the Book of the prophet Daniel:

https://en.wikipedia.org/wiki/Belshazzar%27s_feast

Belshazzar Sees Mysterious Handwriting on a Wall

Book of Daniel 5:1~5:30 (Quoted from the NET Bible)
While Belshazzar, the king of Babylon, was enjoying a great banquet with a thousand of his nobles using the gold and silver vessels that had been confiscated from the temple, the house of God in Jerusalem, a strange message appeared on the wall:

5:5 At that very moment the fingers of a human hand appeared and wrote on the plaster of the royal palace wall, opposite the lampstand. The king was watching the back of the hand that was writing.
5:6 Then all the color drained from the king's face and he became alarmed. The joints of his hips gave way, and his knees began knocking together.
…
5:16 [King Belshazzar] I have heard that you are able to provide interpretations and to decipher knotty problems. Now if you are able to read this writing and make known to me its interpretation, you will wear purple and have a golden collar around your neck and be third ruler in the kingdom.

Daniel Interprets the Handwriting on the Wall

5:17 But Daniel replied to the king, “Keep your gifts, and give your rewards to someone else! However, I will read the writing for the king and make known its interpretation.”
…
5:23 You have exalted yourself against the Lord of heaven. You brought before you the vessels from his temple, and you and your nobles, together with your wives and concubines, drank wine from them. You praised the gods of silver, gold, bronze, iron, wood, and stone - gods that cannot see or hear or compre-hend! But you have not glorified the God who has in his control your very breath and all your ways!
5:24 Therefore the palm of a hand was sent from him, and this writing was inscribed.
5:25 “This is the writing that was inscribed: MENE, MENE, TEQEL, and PHARSIN.
5:26 This is the interpretation of the words: As for mene - God has numbered your kingdom's days and brought it to an end.
5:27 As for teqel - you are weighed on the balances and found to be lacking.
5:28 As for peres - your kingdom is divided and given over to the Medes and Persians.”
5:29 Then, on Belshazzar's orders, Daniel was clothed in purple, a golden collar was placed around his neck, and he was proclaimed third ruler in the kingdom.
5:30 And in that very night Belshazzar, the Babylonian king, was killed.
5:31 So Darius the Mede took control of the kingdom when he was about sixty-two years old.

[The Writing on the Wall, by Dutch artist Rembrandt van Rijn 牆上的字跡, 荷蘭畫家的作品: 林布蘭 (Taiwan), 伦勃朗 (PRC)]

牆上的字跡

5:5 當時，忽有人的指頭顯出，在王宮中燈台對面的粉牆上寫字。王就看著寫字的手背。
5:6 之後，王就臉色蒼白，心意驚惶；腰骨好像脫節，雙膝彼此相碰。
…
5:16 「我聽說你善於講解，能解疑惑。現在你若能讀這文字，把講解告訴我，就必身穿紫袍，項戴金圈，在我國中位列第三。」

但以理解釋牆上的字

5:17 但以理回答王說：「你的贈品可以歸你自己，或給別人。我卻必為王讀這文字，
把講解告訴王。
…

5:23 你竟向天上
的主自高。你將他殿中的器皿拿到你面前，你和大臣、皇后、妃嬪用這器皿飲酒。你又讚美那不能看、不能聽、無知無識的金、銀、銅、鐵、木、石的各神。你卻沒有將榮耀歸與那手中掌管你氣息，和你一切行動的神。
5:24 因此，從神那裏派來手掌和寫下這些字。
5:25「所寫的文字是：彌尼，彌尼，提客勒，烏法珥新。
5:26 講解是這樣：彌尼，就是神已經數算你國的年日到此完畢；
5:27 提客勒，就是你被稱在天平裏，顯出你的虧欠；
5:28 毘勒斯，就是你的國分裂，歸與瑪代人和波斯人。」
5:29 伯沙撒下令，人就把紫袍給但以理穿上，把金圈給他戴在頸項上，又傳令使他在國中位列第三。
5:30 當夜，巴比倫王伯沙撒被殺。
5:31 瑪代人大利烏年約六十二歲，取了國位。