(CNN) -- A second man has been charged with murder in the 2011 disappearance of Tennessee nursing student Holly Bobo.
Other suspects can expect police to be "on their doorstep" soon, Tennessee's top investigator told reporters Tuesday.
Jason Wayne Autry, who is already in prison for an unrelated assault conviction, was indicted on especially aggravated kidnapping and first-degree murder charges by a special grand jury Tuesday, Tennessee Bureau of Investigation Director Mark Gwyn said at a news conference in Decaturville Tuesday afternoon.
Autry, 39, was a longtime friend of Zachary Adams, 29, who was indicted last month on the same kidnapping and murder charges, Gwyn said. Autry, from Holladay, Tennessee, has a lengthy criminal history, he said.
Bobo was 20 when she was last seen on April 13, 2011. Her brother told authorities he saw a man in camouflage leading her away from their home in the small town of Darden, Tennessee.
Information from "several witnesses" led to charges against Autry, Gwyn said.
Investigators "believe there are more people with information and possible involvement," Gwyn said. He told reporters to "expect more announcements in the coming days and weeks."
"These individuals know who they are, and I'm sure they are watching, and they can expect us to be on their doorstep pretty soon," Gwyn said.
Although Gwyn has previously declined to say whether any remains have been found, he acknowledged Tuesday that her body has not been located.
Investigators are "doing everything we can to try to get (her family) some closure" by finding Bobo's body, Gwyn said.
The Bobo case rocked the largely rural swath of central Tennessee, from those who knew the young woman to others who rallied behind the effort to find her.
Hundreds of volunteers -- some on horseback and foot, others on all-terrain vehicles -- turned out to hunt for clues in Decatur, Henderson, Henry, Carroll and Benton counties. Many more attended memorial services or offered supportive thoughts online via groups on Facebook. More than $450,000 has been offered in reward money.