MIAMI (CBSMiami/AP) – Federal officials said a Florida man had been sentenced to three years in federal prison for mailing a threatening letter to the federal courthouse in Miami.

Court records show 47-year-old Freddy Velazquez mailed the letter in February 2019 containing a powder substance from state prison in Monticello, Florida. He was serving a sentence there for a prior conviction.

The U.S. attorney’s office in Miami said in a news release Friday that the letter including writing saying there were “chemicals that are going to kill many of you…I hate all of you pigs and hope you all die. I fight you all till you all die.”

After a courthouse employee opened the letter, the building was evacuated and nearby streets closed down for about eight hours. Four federal law enforcement agencies and Miami police hazardous materials unit responded to the possibility of a biological threat.

The substance turned out to be detergent that was not dangerous.

Velazquez pleaded guilty in February of this year to mailing a threatening communication.

(© Copyright 2020 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)