Recap: Tesla has been going through a difficult time lately, facing safety questions over its Autopilot system, layoffs, and production issues with its Model 3. But according to CEO Elon Musk, some of its problems were the result of internal sabotage by an employee, who may not have been working alone.

CNBC obtained an email sent by Musk to every Tesla worker on Sunday. It says that the staff member in question had admitted to "quite extensive and damaging sabotage to [Tesla's] operations," which includes the modifications of the "Tesla Manufacturing Operating System under false usernames," and sending "large amounts of highly sensitive Tesla data to unknown third parties."

The employee, who is now being questioned by the company, says he was angry over not receiving a promotion. Musk says this was the right move, "in light of these actions."

A disgruntled worker taking out their anger on an employer isn't unusual, but Telsa and Musk are investigating whether this person was working with outside entities, such as "Wall Street short-sellers" or "oil & gas companies." The CEO also questions if "the multitude of big gas/diesel car company competitors" were involved. "If they're willing to cheat so much about emissions, maybe they're willing to cheat in other ways?" he wrote.

Musk sent a separate email addressed to everyone at his company yesterday. In it, he talks about "another strange incident that was hard to explain": a small fire at the Fremont facility on Sunday---the fifth since 2014. While he says this could be a random event, Musk quotes former Intel CEO Andy Grove's "Only the paranoid survive" warning.

Musk's email asks staff to be "extremely vigilant," particularly as Tesla increases the production rate of the Model 3 to 5000 per week. "This is when outside forces have the strongest motivation to stop us," he added.