Matthew Unglesbee was arrested Sunday at his mother’s home in Quincy, according to the account of the investigation. A two-count criminal complaint filed Monday charges him with mailing threatening communications and disseminating false information and hoaxes.

The complaint says Unglesbee admitted sending the envelopes and using table salt because he thought it looked like anthrax. Investigators said he acknowledged knowing the mailings would frighten people in congressional offices, though he described them as a joke to federal agents.

Schneider, a Democrat who represents Illinois’ 10th Congressional District in the northwest suburbs, said his staff spotted a threatening letter with a Quincy return address and a Springfield postmark. The team closed the office mailbox and called police, he said.

Investigators said the mailings copied other recent white-powder letters sent to politicians around the country. The complaint identifies four Illinois lawmakers as recipients, but the available account names only Schneider.

Unglesbee has prior convictions for threatening a public official, impersonating police and sexually assaulting a minor, and has faced violations of sex-offender registration requirements, according to court records and arrest records described in the investigation. The current federal allegations remain accusations; a charge is not a finding of guilt.

The case underscores how threats and hoax substances can disrupt the work of elected officials and prompt law enforcement responses, even when the material is not hazardous.