It was narrated from Abu Musa, may Allah be pleased with him, that the Messenger of Allah (ﷺ) said:
"Indeed, before the Hour of Judgment there will be a Kharj (tribulations)."
I asked, "O Messenger of Allah, what is a Kharj (tribulations)?"
He replied, "Killings."
Some Muslims then said, "O Messenger of Allah, we are already killing such and such a number of polytheists every year."
The Messenger of Allah (ﷺ) said, "No, that is not killing polytheists. Rather, you will be killing one another, so that a man will kill his neighbor, his uncle's son, and his relative."
Some of the people then asked, "O Messenger of Allah, will we have any sense on that Day?"
The Messenger of Allah (peace and blessings of Allah be upon him) replied:
"No, most people of that time will be robbed of their reason, and only weak people who lack reason will remain."
(Sahih Ibn Majah, No. 3213)