An employee of the Federal Aviation Administration was set to appear in federal court on Tuesday on charges of threatening to kill President Trump after allegedly using his government-issued work computer for his plans.

The Justice Department accused Dean DelleChiaie, 35, of Nashua, N.H., of using his work computer in January to conduct a series of suspicious searches, including how to smuggle a gun into a federal building, the details of previous assassination attempts against Mr. Trump, and the phrase “I am going to kill Donald John Trump.”

The criminal complaint against Mr. DelleChiaie was filed on Friday and he was arrested on Monday. If convicted of the charges against him, he faces a term of imprisonment up to 5 years and up to a $250,000 fine.

During a February interview with Secret Service officials, Mr. DelleChiaie admitted to conducting those searches, according to the department. He also confirmed to the Secret Service that he owned three firearms, including a handgun he kept in a safe at home.

According to the department, Mr. DelleChiaie made his plans to harm Mr. Trump explicit in April, in an email from his personal account sent to a public White House email address. In it, he wrote: “I, Dean DelleChiaie, am going neutralize/kill you – Donald John Trump – because you decided to kill kids – and say that it was War – when in reality – it is terrorism. God knows your actions and where you belong.”