Several federal law enforcement sources told CNN the package contained a rambling note that criticized Facebook founder Mark Zuckerberg and the relationship between academic institutions and the developers of virtual reality. CNN has reached out to Facebook for comment. The note was in a hard plastic container and detonated when the victim opened the latches and lifted the lid, the sources said.

The package was delivered to the university's virtual reality center and was opened by someone who works in the center, the sources said.

While the employee who opened the package was not seriously hurt, the explosion caused lacerations to his hands and other injuries, the sources added.