An Arizona man was charged last Thursday in connection with a series of threats made to schools and other institutions in the Omaha area last month.

Andrew Isaac Abrams, of Tucson, Arizona, was charged with transmitting a series of threats in interstate commerce on April 23, Acting U.S. Attorney Jan Sharp said in a statement.

The threats were received at schools in the Millard, Omaha, Elkhorn and Westside school districts. Other threats were received at the Union Pacific Railroad headquarters and the Douglas County Courthouse. Union Pacific evacuated its headquarters.

Law enforcement officials determined quickly that the calls were a hoax and were coming from outside of Nebraska.

Abrams faces up to five years in prison, a $250,000 fine, and up to three years of supervised release for each count of conviction.

Abrams was a former doctor in Arizona who had a history of mental illness and making threats, according to documents relating to the surrender of his medical license, The Omaha World-Herald  reported. It was unclear if he had any connection to Omaha.