Andrej Karpathy, a high-profile Tesla executive who played a key role in developing the electric car maker’s artificial intelligence and driver assistant technology, said on Wednesday he is leaving the company.

The departure of Karpathy, who provided no reason for leaving, comes at a critical time as Tesla Chief Executive Elon Musk races to achieve full self-driving capability this year, after missing earlier targets several times…

The departure of Karpathy, whose title was senior director of AI, came after Tesla on Tuesday said it was shutting its office in San Mateo, California, part of the company’s team developing “Autopilot” driver assistant technology, and laying off over 200 people there…

“I would imagine that there will be an internal promotion to fill Karpathy’s position. It would not be easy to get somebody externally with Karpathy’s experience and knowledge,” said Raj Rajkumar, professor of electrical and computer engineering at Carnegie Mellon University.