What We Know About the Packages Sent to Friends by FSU Shooter Myron May sent eight packages the day before his shooting rampage.

 -- Federal authorities have intercepted several packages they suspect were mailed to eight acquaintances by Myron May before he went to the Florida State University where he shot three people and was killed by police.

At least one of the envelopes contained a thumb drive, a law enforcement source to ABC News.

The packages were believed to have been mailed to eight people on Wednesday, the day before May went to Strozier Library on the Tallahassee campus about 12:30 a.m. and opened fire. Three people were wounded and May was killed by police when he emerged from the building.

Those packages are starting to be collected. The FBI said they picked up a package that was addressed to a location in northern Virginia. The package was confiscated up before being delivered.

Joe Paul, who attended FSU with May and lives in Virginia, told ABC affiliate that he was one of eight people on a group message from May. Paul did not know the other people on the list.

A law enforcement source said the "packages" are large envelopes. They do not contain any threats or dangerous materials, officials said. At least one envelope contained a thumb-drive, ABC News has learned.

Police have told the recipients not to open the packages once they arrive but to notify law enforcement.

The U.S. Postal Service said today that it was aware of May's mailings and said it is "taking steps to ensure the safety of postal customers, employees, and facilities. To date, letters identified do not pose a threat or contain hazardous items."

Tallahassee police told ABC News that they suspect the packages contain journals and videos detailing May's belief that police were spying on him and that the government was out to get him.

Paul said it was unnerving to get the message from May.

"We're a little afraid," Paul said. "Why did he chose us?"

In the message, May wrote "I sent the packages today. The expected deliveries are Friday," with pictures of each of the Priority Mail envelopes attached.

"What did he send everyone? Was it a manifesto? Was it a message? I don’t know. I think I’m just as curious as everyone else," Paul said in the WSB-TV interview.

May, 31, grew up as a foster child, but succeeded and became a lawyer. He began to deteriorate in September and October, according to police reports in Las Cruces, New Mexico, where he worked for the district attorney. The police reports said that May was convinced that police had planted cameras in his home and car and that he was hearing voices in the walls. May's ex-girlfriend told police that she feared he would harm himself.

May recently resigned his job with the district attorney and in the weeks before his attack at the library May had returned to the foster home where he grew up in Tallahassee.