Martin Shkreli. REUTERS/Carlo Allegri (Reuters) - A U.S. judge on Wednesday ordered Martin Shkreli to be jailed while he awaits sentencing for securities fraud, citing a Facebook post in which the former drug company executive nicknamed the “Pharma Bro” offered a $5,000 reward for a strand of Hillary Clinton’s hair.

U.S. District Judge Kiyo Matsumoto in Brooklyn said the Sept. 4 post, which prompted a call from the U.S. Secret Service, showed Shkreli posed a danger to the public that warranted revoking his $5 million bail. U.S. prosecutors had moved to jail Shkreli last Thursday.

Shkreli apologized for his actions on Monday.

In a letter addressed to Judge Matsumoto, Shkreli wrote that he "used poor judgment" and "never intended to cause alarm or promote any act of violence."

"I wanted to personally apologize to this Court and my lawyers for the aggravation that my recent postings have caused," Shkreli wrote. "I understand now, that some may have read my comments about Mrs. Clinton as threatening, when that was never my intention when making those comments."

Shkreli, who was found guilty on two counts of securities fraud, caught the Secret Service's attention after he wrote a Facebook post last week that read: "The Clinton Foundation is willing to KILL to protect its secrets. So on HRC's book tour, try to grab a hair from her... Will pay $5,000 per hair obtained."