The FBI says it’s close to ending its investigation of the 2001 anthrax mailings, after concluding the main suspect, Dr. Bruce Ivins, acted alone. Ivins killed himself last week after learning he faced charges in the anthrax letter attack that killed five people. On Wednesday, government officials released documents showing Ivins had a near-perfect match of anthrax spores around the time of the mailings and had also spent hours working late nights in his lab before the anthrax was mailed. Ivins was also found to have sent emails with language similar to the threats found in the letters. FBI official Joe Pershini said Ivins was acting alone.

Joe Pershini: “Painstaking investigation led us to the conclusion that Dr. Bruce E. Ivins was responsible for the death, sickness and fear brought to our country by the 2001 anthrax mailing and that it appears, based on the evidence, that he was acting alone.”

The government’s case against Ivins has come under wide criticism. The evidence remains entirely circumstantial, and investigators have been unable to connect Ivins to being in New Jersey, where the letters were mailed.