"Our field tests indicate it was ricin. Our lab tests confirm it was ricin. So I don't get why others are continuing to use equivocal words about this," Gainer said.
Preliminary field tests can often show false positives for ricin. Ricin is derived from the castor plant that makes castor oil. There is no antidote, and it's deadliest when inhaled. The material sent to Wicker was not weaponized, Gainer said.
An FBI intelligence bulletin obtained by The Associated Press said the two letters were postmarked Memphis, Tenn.
A Mississippi state lawmaker, Democratic Rep. Steve Holland of Plantersville, said Wednesday night that his 80-year-old mother, Lee County Justice Court Judge Sadie Holland, received a threatening letter last week with a substance that has been sent to a lab for testing. He said this letter was also signed "K.C."
"She opened it herself" on April 11 and told Holland about it three days later, Holland said.
He said she had not been to the doctor, but he planned to take her Thursday.
"She's fine," Holland said. "She's had no symptoms."
Curtis' neighbors, who said he did not seem violent, were concerned about their safety Thursday and worried by the idea that someone was making poison in a house that sits so close to their bedrooms and front yards. The one-story, single-family home is similar to the others in the neighborhood — red brick with white trim.
A church, and a community center with an outdoor children's play area, are just steps from Curtis' house. The home also is near an area with several mailboxes for the community. But neighbors said they rarely saw him retrieve mail and didn't speak with him much.
"He was quiet. He pretty much stayed to himself," said neighbor Lacey Ross, 29.