The strange case of Ryan Kelly Chamberlain II got even stranger yesterday after court documents in the case of the now-captured political activist were made public. On the run for a short period, during which he posted what had appeared to be a suicide note on social media, police and the FBI caught Chamberlain on Monday after patrons at a local bar recognized him from television coverage. Now we know why the FBI took an interest in the former social-media consultant in the first place:

Bomb technicians found a series of items in his house, leading to a manhunt that ended with his arrest Monday. Items included a powdery, green explosive substance, a model rocket motor, ball bearings and an igniter for home-made bombs, according to a different affidavit unsealed earlier this week. It did not list deadly toxins at the time.

But the latest documents detail lethal poisons bought anonymously in dark, encrypted corners of the Web.

“The investigation has revealed that Chamberlain has utilized an anonymous, Internet-based market place known as Black Market Reloaded to facility the unlawful acquisition and possession of biological agents and lethal toxins in California and Florida,” FBI agent Michael Eldridge wrote in the latest documents.

Chamberlain bought abrin from a seller in Sacramento in December, the documents allege. He said he planned to use the poison to “ease the suffering” of cancer patients, according to the documents.

The FBI followed up with the seller in May:

In May, agents questioned a Black Market vendor of toxins, improvised explosives and guns from Sacramento who told agents that he had done business with Chamberlain. The seller said Chamberlain asked for samples of pure abrin to help ease the suffering of cancer patients, according to the affidavit.

The vendor instead sold him two clear vials of ground rosary peas, which can be converted into abrin, the affidavit said. The vials contained enough peas to create hundreds of lethal doses of the toxin.

There is no antidote for abrin, either. Chamberlain apparently represented himself as someone who wanted to help cancer patients, but as KTVU reports, he also asked questions about whether abrin was detectable in an autopsy on someone who had been killed with it:

Chamberlain also bought enough pure nicotine to use in a lethal attack, according to the court records.

These developments still leave a few questions. If Chamberlain bought these in December and the FBI began its investigation in May, that seems like a long time for Chamberlain to have held onto this stuff without trying to use it — unless they suspect that he might have used it, but for now no connection to any suspicious death has been alleged. The investigation started with a raid on the seller, which turned up the records of the sale to Chamberlain, so this might be a case of pure luck in finding a potential domestic terrorist — or is it just a case of clinical depression? That’s the argument Chamberlain’s lawyers made in court:

The lack of an actual attack might demonstrate that the purchase was part of a clinical pathology rather than an intent to commit terrorist acts, but we don’t know what else the FBI might have found on that investigation, either. If it was the former, why would Chamberlain have been so particular about getting pure abrin — to the point of buying his own rosary peas to make it himself? On the other hand, why go for something so exotic that any personal connection to it would tend to be prima facie evidence of guilt? Pathology, or just stupidity?