Sad news for Silicon Valley: A Stanford computer science professor who served as a key mentor to Google’s founders was found dead in his pool at the age of 47. Google founders Sergey Brin and Larry Page worked with Rajeev Motwani as PhD students. “Today, whenever you use a piece of technology, there is a good chance a little bit of Rajeev Motwani is behind it," Brin wrote on his blog. The three wrote a paper in 1998 that detailed the development of the now-ubiquitous search engine. A university spokesman said the cause of death is unknown. Motwani didn’t know how to swim, and some have speculated he fell into the pool when wandering around at night, since he often worked late.