A webmaster posted an issue in the Google Webmaster Help forums with the Google URL Removal tool.

In short, the site he is working on was hacked. He is using the tool to manually remove the hacked pages from Google, one by one. But for some reason, one of the URLs he entered triggered not just one page to be removed but all.

He asked:

Here is a screen shot:

John Mueller from Google responded in the thread saying:

It might be the configuration of the hack, confusing Google? I am unsure.

Forum discussion at Google Webmaster Help.