The Secret Service acknowledged late yesterday that the White House received a letter that an initial test showed positive for cyanide. So far, the tests have not reached a conclusion, but as NBC News reports, they’re taking it seriously. It doesn’t appear to be so much a terrorist attack as a longtime threat resurfacing, according to one report:

An envelope mailed to the White House tested positive for cyanide, the Secret Service said.

The envelope arrived on Monday at a facility elsewhere in the Washington area that screens mail for the White House. Biological tests were negative, but a chemical test on Tuesday came back positive for cyanide, the agency said.

The envelope was sent to another facility to confirm the result.

The Intercept, which broke the story last night, says that the return address looked pretty familiar to Secret Service investigators:

The envelope listed a return address for a man who the alert says has a record with the Secret Service dating back to 1995, which includes sending a package covered in urine and feces.

That person has sent multiple packages over the years; the most recent package was received on June 12, 2012, which contained mini alcoholic beverages.

“An envelope containing an unknown milky substance, in a container wrapped in a plastic bag, received at the White House Mail Screening Facility, tested positive for Cyanide,” the alert states.

Jana Winter reports in an update that the Secret Service isn’t talking much about whether they’ve located the suspect or if they’ve taken him into custody. The entire situation sounds a little strange. There’s nothing illegal about mailing packages to the White House, but it’s at least curious behavior, especially when the items are rather unusual, such as mini-bottles of booze. One would think that urine and feces would be illegal to ship anywhere except for medical purposes and only under strict seal, though, so why wasn’t Mr. Poopy Pants picked up at that point in time?

For that matter, why would he switch to an outright attempt to poison someone after twenty years of just being a weirdo? That might be easier to explain; perhaps the earlier packages just didn’t work to satisfy the compulsion any longer, or maybe the meds stopped working. Either way, if this turns out to be confirmed, the suspect has gone from being a 20-year crank to a real danger to others. Let’s hope they find him soon for everyone’s sake, not least his own.