BOSTON — Federal authorities say a Massachusetts man tried to hire a hit man to kill three people, including a police officer, while he was in jail on multiple cases.

Twenty-year-old Mason Stickney pleaded not guilty Tuesday in Boston federal court to charges of using an interstate commerce facility in the commission of murder-for-hire.

Prosecutors say the hit man Stickney allegedly worked with in November was an undercover FBI agent. The alleged targets were not harmed.

They say a fellow inmate at the Essex County House of Corrections had alerted authorities to the plot in October after Stickney solicited his help in the scheme, offering $10,000.

It’s unclear why the three people were allegedly targeted.

Stickney’s federal public defender didn’t immediately respond to an email seeking comment Tuesday.