Tammy Steffen has been sentenced to almost five years in prison for cyberstalking

Highlights Threats came from 369 Instagram accounts, 18 different email addresses

Threats from these Instagram accounts was controlled by 1 woman

FBI: Fitness trainer used these accounts to harass ex-business partner

The threats came from 369 Instagram accounts and 18 different email addresses. But they were all controlled by one woman.

FBI agents say fitness trainer and mother of four Tammy Steffen used those accounts to unleash a torrent of harassment on her ex-business partner at a Tampa, Florida, gym and on her competitors in the bodybuilding world.

"I plan to slice you up into little pieces," read one message sent from an innocuously named Instagram account, catloverexpress. "Your blood shall I taste."

On Friday, the 37-year-old woman was sentenced to almost five years in prison after pleading guilty to federal charges of cyberstalking and sending threatening communications online.

"The extent of her crime is astounding," FBI special agent Kristin Rehler told WFLA.

But the cyberstalking, which targeted five victims in three states, is just one aspect of a strange saga. Authorities say Steffen, 37, also deployed a headless baby doll and a fake kidnapping scheme to try to exact revenge on her former business partner. The reason? She believed he had sabotaged her chances of winning an online fitness competition - an allegation authorities said is untrue.

It started with the headless doll. On July 9, 2018, Steffen called the sheriff's office to report that someone had left the ominous item on the front porch of her two-story house in the Tampa suburb of Holiday, according to an arrest report. Inside the doll was a note: "New toy for the kids."

Five days later, Steffen phoned the sheriff's office again - this time to tell them someone had tried to kidnap her daughter. The 12-year-old girl had been feeding the family's dogs when, Steffen said, a Hispanic man had tried to snatch her and drag her into the woods. The child had urinated on herself out of fear.

Steffen led deputies to the place where she said the purported kidnapping had occurred, and pointed out a laptop case hidden in the brush. Inside was a notepad filled with personal information on Steffen and her home. The girl described her attacker, and her mother named the former business colleague as a potential suspect. Authorities took the report seriously, using helicopters and dogs to search the woods.

But deputies became suspicious when the child "questioned what would happen to [her mother] if she told the truth." They uncovered Walmart surveillance footage showing that Steffen had purchased the laptop cover and blue notebook. They concluded she had even forced her daughter to urinate on herself in a bid to make the story more believable, and had concocted the scheme after planting the headless doll didn't net the response she wanted.

"You get false reports quite frequently," Pasco County Sheriff's Office spokesman Kevin Doll said. "To the extent that this woman went? Not to that extent. And from what she claims is the reason for doing it, that's even more puzzling."

"You're talking 10 to 20 people for a number of days investigating this and subsequent reports that she had made," Doll said.

Steffen was arrested July 17 on charges of filing a false police report, tampering with evidence and child neglect. Deputies added witness tampering charges days later, after she called her daughter from a recorded jail phone line and told her to claim responsibility for the kidnapping plot.

"You won't get in trouble," Steffen told her daughter, according to a report, "but I will."

In fact, the trouble was just beginning for Steffen. In November, federal agents arrested her on the stalking charges. According to the criminal complaint, she sent hundreds of messages to individual victims, the former business partner among them. She also tried to discredit them professionally and made threats to their lives and the lives of their families and friends.

"All hell is gonna rain fire down on your world like never seen before," one January 2017 message read. "You have picked the wrong person to mess with. You have no idea what you've done. I will be catching the next flight to Michigan out of here."

In another instance, the FBI said, Steffen called the business owned by a Collier County, Florida, woman so many times that the company was unable to receive calls from customers. She also changed the business's voice-mail message to "sounds of a sexual nature, including people moaning in the background."

Steffen's messages and calls caused "substantial emotional distress" to the victims, who saw them as true threats, the FBI said.

She had no criminal record before 2018 according to her attorney, Keith Hammond, who declined to comment on the case. The fitness expert, who will begin her 57-month sentence for the cyberstalking charges after serving just under a year in jail for the false kidnapping incident, wrote in a letter to the judge that she was sorry for her actions.

"While no one wants to have legal proceedings," she wrote, "I am thankful for the intervention in my life."