The Destruction of Nalanda, as chronicled in the Tabaqat-i-Nasiri by the Persian historian Minhaj-i-Siraj written a couple of decades after Bhaktiyar Khilji's death [1]:
"There were two brothers of Farghanah, men of learning, one Nizam-ud-Din, the other Samsam-ud-Din [by name], in the service of Muhammad-i-Bakht-yar; and the author of this book met with Sam-sim-ud-Din at Lakhanawati in the year 641 H., and this account is from him.
These two wise brothers were soldiers among that band of holy warriors when they reached the gateway of the fortress and began the attack, at which time Muhammad-i-Bakht-yar, by the force of his intrepidity, threw himself into the postern of the gateway of the place, and they captured the fortress, and acquired great booty.
The greater number of the inhabitants of that place were Brahmans, and the whole of those Brahmans had their heads shaven; and they were all slain.
There were a great number of books there; and, when all these books came under the observation of the Musalmans, they summoned a number of Hindus that they might give them information respecting the import of those books; but the whole of the Hindus had been killed.
On becoming acquainted [with the contents of those books], it was found that the whole of that fortress and city was a college, and in the Hindu tongue, they call a college Bihar.
When that victory was effected, Muhammad-i-Bakht-yar returned with great booty, and came to the presence of the beneficent Sultan, Kutb-ud-Din, I-bak, and received great honour and distinction."
1. https://archive.org/details/tabaqat-i-nasiri-volume-1/page/5...