SAN DIEGO -- An Encinitas man will be tried in federal court for allegedly making a series of bomb threats targeting a University of California, San Diego research building where he worked before being fired, and planting a mock explosive device in the facility, authorities said Monday.

Members of a terrorism task force arrested Richard Sills Jr., 54, on Friday in connection with the Dec. 5 crimes, which prompted evacuations at the La Jolla campus, according to the FBI.

Sills, a temporary employee in the UCSD Biomedical Science Building, was the second person arrested in the case.

Last week, prosecutors dismissed charges against 50-year-old Timothy Bryon Kalka, of San Diego, who had been booked Dec. 8 on suspicion of carrying out the hoax.

Kalka was implicated by at least one person who heard an audio recording of one of the threats and told investigators the voice apparently was his, the FBI reported.

Kalka had worked as a researcher in the targeted building until Nov. 30, when he was fired, officials said.

Kalka called his incarceration a “nightmare.”

“I think that the F.B.I is unbridled,” Kalka said. "If you do that to someone, at least have some real solid evidence.”

The F.B.I has apologized to Kalka, but he says he’s considering filing a lawsuit.

Authorities did not immediately disclose evidence that allegedly links Sills to the crimes.

Sills is scheduled to make his initial appearance in federal court in downtown San Diego Tuesday afternoon, according to the FBI.