A Massachusetts man was arrested on federal hoax-related charges with sending letters with white powder to five people, including one to Donald Trump Jr. that landed his wife, Vanessa Trump, in the hospital, the U.S. Attorney’s Office in Massachusetts announced Thursday.

Daniel Frisiello, 24, is accused of mailing five envelopes early last month with threatening messages and a white substance, which turned out to be nonhazardous. The envelopes were postmarked in Boston.

"These kind of hoaxes may not cause physical harm, but they scare the heck out of people," said Andrew Lelling, U.S. attorney for Massachusetts.

Federal authorities said one of the letters containing powder was sent to Antonio Sabato Jr., the Republican former underwear model and soap opera actor who is running for a U.S. House seat in California.

Other recipients were Debbie Stabenow, the Democratic U.S. senator from Michigan; Nicola Hanna, an interim U.S. attorney in California; and Michele Dauber, a Stanford University law professor who has promoted the effort to recall the judge who presided over the Brock Turner sexual assault case.

The letter sent to the president's son was opened by Vanessa Trump. It contained seven short sentences and was rife with curses and insults, officials familiar with the case told NBC at the time.

"You are an awful, awful person. I am surprised that your father lets you speak on TV. You the family idiot. Eric looks smart," the letter read, according to officials familiar with the case. "This is the reason why people hate you. You are getting what you deserve. So shut the f--- up.”

Trump's daughter-in-law called 911 and reported she was coughing and nauseous. She was taken to New York Presbyterian-Weill Cornell Medical Center strictly as a precaution.

Trump Jr. married Vanessa Trump, formerly Vanessa Kay Haydon, in November 2005 at Mara-a-Lago. Trump Jr.'s aunt officiated. The couple has five children; none of the kids were home at the time of the incident.

It was not the first time a Trump has received white powder in the mail. In March 2016, police detectives and FBI agents investigated a threatening letter sent to the Manhattan apartment of Donald Trump Jr.'s brother, Eric, that also contained a white powder that turned out to be harmless. Envelopes containing white powder were also sent to Trump Tower, twice in 2016.

Hoax attacks using white powder play on fears that date to 2001, when letters containing deadly anthrax were mailed to news organizations and the offices of two U.S. senators. Those letters killed five people.

In a statement, Catholic Charities of Boston confirmed Frisiello is an employee, and has been placed on immediate leave. A spokesperson said the charity is cooperating with the investigation.

"The FBI has assured us that the charges do not involve any activity in his role at Catholic Charities but concern alleged threats against a political figure," the charity said in a statement. "As a matter of background, Catholic Charities processed the appropriate background checks when the employee was hired."

This is a developing story. Check back for updates.