St. Louis County Prosecuting Attorney Robert P. McCulloch speaks during a news conference discussing charges issued against Adam Michael Capriglione Tuesday, April 15, 2014, in Clayton, Mo. Capriglione, 29, of south St. Louis County, has been indicted on 19 felony charges that include forcible rape, forcible sodomy and felony domestic assault. (AP Photo/Jeff Roberson)

WASHINGTON -- St. Louis County Prosecuting Attorney Robert McCulloch stated definitively on Thursday that a Twitter account claiming inside knowledge of the grand jury deliberating whether to charge the police officer who killed Michael Brown "had, indeed, been hacked." But a spokesman for McCulloch revealed that his conclusion was based solely on an interview with the St. Louis County woman associated with the account and a search of her computer.

Susan M. Nichols had operated a Twitter account under the name @thesusannichols. In early October, a tweet sent from the account indicated that the user knew "someone sitting on the grand jury of this case" and that there wasn't enough evidence to charge Ferguson, Missouri, Police Officer Darren Wilson in Brown's death. The message was quickly deleted, and Nichols began telling multiple media outlets that her account had been hacked and that she had not used it in months.

McCulloch said after the possible leak that he would be "shocked if a member of the grand jury said anything." On Thursday, he announced that his office had concluded that the account was hacked "and the origin/author of the tweet is unknown."

McCulloch spokesman Ed Magee told The Huffington Post that Nichols had voluntarily spoken with investigators and never went under oath. While Nichols also allowed investigators to look at her computer, they did not examine her cell phone or any other electronic devices she might own, Magee said.

"She said she has nothing to do with it, and that's what we went by and we couldn't prove otherwise," Magee said. "She was very cooperative, came in and talked to us." She didn't have a lawyer, he said.

McCulloch's office subpoenaed Twitter for information about @thesusannichols, but the company said it didn't have IP logs affiliated with the account, according to Magee. (Twitter's website says some information like IP logs "may only be stored for a very brief period of time.") Investigators did not look for information associated with @smde7763, the Twitter handle that @thesusannichols adopted shortly after attention was called to the original username, because Magee said it was "a different account." (But the two Twitter handles have seemingly identical histories of tweets going back over a year.)

Magee said the investigation was complicated by the fact that there was "no crime that she committed" and that Nichols was talking to the office voluntarily. McCulloch's statement on Thursday said that Nichols "has no connection with any member of the grand jury."

Before @thesusannichols sent out the tweet claiming insider knowledge about the grand jury, the account was actively discussing what was happening in Ferguson. Whoever was operating the account under Nichols' name claimed to be wearing a bracelet in support of Officer Wilson in late September. "Here's a thought. Don't raise your kids to be thugs. #Ferguson," the account said in late August. Amid tweets about the 16th season of the reality show "Big Brother" and retweets about #Benghazi, the account also said that protesters "disgrace the STL [St. Louis] name."