A man charged with possessing explosive material at his San Francisco apartment also used an anonymous, Internet-based marketplace to try to buy biological agents and lethal toxins, the FBI said in documents unsealed Friday.

In the search warrant affidavit, FBI Special Agent Michael Eldridge said witnesses reported shipping the poison abrin to suspect Ryan Chamberlain.

It was unclear, however, if Chamberlain ever received the poison that is found in the seeds of a plant called the rosary pea.

Authorities have not said what, if anything, Chamberlain intended to do with the toxins or with the bomb-making materials found at his apartment.

Chamberlain said he wanted to use the abrin to ease the suffering of cancer patients, according to the affidavit.

The 42-year-old Chamberlain was arrested Monday after a three-day manhunt that authorities said was prompted by the discovery of bomb-making materials at his apartment.

Chamberlain apparently came to the attention of the FBI as it investigated and monitored the online marketplace where people allegedly bought and sold guns, bombs, drugs, chemicals and counterfeit goods.

Also on Friday, U.S. Magistrate Judge Nathanael Cousins refused to let Chamberlain post bail pending his trial, which has not yet been scheduled.

Chamberlain has been charged with one count of possessing material that could be used to build an explosive device. He has not entered a plea. His public defender declined comment outside court.

The judge scheduled an afternoon hearing to determine whether to transfer Chamberlain to a secured psychiatric unit at a hospital, where he could undergo an exam.