MINDY MCCREADY committed suicide after learning she was at the center of an FBI inves­tigation into her live-in lover’s mysterious death, and that she was losing custody of her two young sons.

Those are the shocking revelations of an extensive ENQUIRER inves­tigation into the tragic death of the 37-year-old singer, who shot herself and her late lover David Wilson’s dog on the front porch of her Arkansas home on Feb. 17.

Even more appalling, her former fiance be­lieves McCready would have killed her sons Zan­der, 6, and 10-month-old Zayne if they’d been with her!

“Just look at what she did and how she did it,” Zander’s father Billy McKnight, lead singer of the popular country rock group Soul Circus Cowboys, told The ENQUIRER in an exclusive interview.

She killed the dog before she killed herself, and I fear she would have taken those kids with her too, if they’d been there.”

Chillingly, authorities investigating the deaths of Wilson and McCready, who left a treatment facility just days before her suicide, are probing that possibility.

“One of the working police theories is that Mindy was hatching a plan to get the kids when she got out of the treatment facility,” a source close to the investigation told The ENQUIRER.

“Had she done so, those children could have been part of a triple death plot.”

Fortunately, the two youngsters had been in foster care since Feb. 6. That’s when McCready was involuntarily committed to a mental health facil­ity after her father told a court that she’d been self-medicating with booze and prescription pills after Wilson’s death.

Wilson, a 34-year-old music producer and Zayne’s father, was found bleeding from the head by Cleburne County Sheriff ’s deputies on the front porch of the couple’s plush lakeside home in Heber Springs, Ark., on Jan. 13.

He reportedly died of a self-inflicted gunshot wound, but in a blockbuster exclusive, The ENQUIRER was the first media out­let to report that cops had not ruled out murder in Wilson’s death.

At the time, Cleburne County Sher­iff Marty Moss said that McCready was not a suspect in her lover’s death, but pointed out: “If you’ll notice, it was Mindy McCready’s spokesperson – not anyone involved in the investigation – who made the determination that Mr. Wilson’s death was due to a self-inflicted gunshot wound.”

In a “Today” Show interview that aired Jan.29th, McCready denied any involvement in Wilson’s death.  But shortly after she was released from the treatment center into an outpatient clinic on Feb 8, FBI agents questioned her about the Cleburne County Sherrif’s probe into Wilson’s death, according to private investigator Dan Hanks.

“Mindy was very upset that police would not clear her name, Hanks, a longtime friend of McCready, told The ENQUIRER.

And another pal blames the country thrush’s suicide squarely on the police invstigation.

 “Mindy was afraid that the cops were going to determine that she had something to do with David’s death. I believe that’s the reason she killed herself!” her former personal assistant Steve Darling, who lived and worked with her in Nashville, told The ENQUIRER.

“Detectives interviewed me be­cause they believed there were unanswered questions about the way David died.”

Hanks, one of the the last people to talk to McCready, shed more light on the events surrounding Wilson’s death and the couple’s last days together.

According to McCready, Wilson disappeared two days before his sui­cide after the couple argued over his addiction to Internet pornography and his purchase of an expensive truck, Hanks said.

“When he came back home, Mindy said that David told her he’d cheated on her and begged forgive­ness,” revealed Hanks. “But he said the cheating was a reference to the pornography, not an affair with another woman.”

On the night Wilson died, Mc­Cready was in the bedroom with her sons, according to Hanks.

“Mindy said that she heard the dog break through the screen door, barking and tearing things up,” Hanks told The ENQUIRER. “She said when she went out onto the front porch, ‘There he was with his brains splattered all over the place.’

“When cops ar­rived, David was still alive. Mindy wanted to go with him in the am­bulance, but police took her in for questioning. She said they ran a gunshot residue test on her hands to determine if she’d fired a gun, but it came out negative.

“David died while Mindy was with the police. When they took her back to the house, they asked her where the bullet was that had killed David. David’s dog spit the bullet out at the cops’ feet.”

McCready never recovered from Wilson’s death, Hanks said, and less than 48 hours before her own suicide, the Arkansas Department of Human Services served her with a legal notice that they intended to award custody of her sons to her mother and stepfather, Gayle and Michael Inge.

“This is what pushed her over the edge,” Hanks told The ENQUIRER.

“She was terrified that she would lose her children. It was only a proposed settlement, but Mindy believed it was a done deal, and she would never have her children with her again.”

For McCready, losing her sons was the final unbearable chapter follow­ing years of pain, friends say.

After soaring to fame with her 1996 debut album, “Ten Thousand Angels,” McCready’s career went into a downward spiral as she struggled with personal demons.

Repeated arrests for drug use, DUI, probation violations and an arrest af­ter a scuffle with her mother bounced her in and out of jail. A sex tape and scandal involving an alleged teen­aged affair with baseball great Roger Clemens kept her name in the news.

McCready attempted suicide with drugs at least three times before the fateful day, when a neighbor heard the gunshots that claimed her life.

“I was working in my garage when I heard the first gunshot,” the neighbor, who called police, told The ENQUIRER.

“It sounded like the shot was muf­fled or maybe from a smaller caliber gun. I walked to the garage door and looked toward Mindy’s house, where the shot had come from.

“Then, about 12 to 15 seconds later, there was a second shot that was much louder than the first.”

The day she died, a caring neigh­bor had brought her a big container of pasta. But Mindy wouldn’t open the door, so the neighbor just left it on the porch.

The net day, an ENQUIRER re­porter was at the scene when four Cleburne County Sheriff investiga­tors carried evidence bags from the death house. One investigator also hauled out a dog bed containing two puppies.

“Those puppies were offspring of the dog that Mindy shot and killed,” a law enforcement source revealed.

“The dog belonged to David. She always despised it because it was very mean and aggressive toward her and anyone that came near it.”

The ENQUIRER has also obtained a chilling 2 1/2-page “suicide note” that McCready wrote before a drug overdose in 2005. She survived that suicide bid, but her heartfelt words still ring eerily true eight years later.

She wrote: “I have tried to love people and give of myself till it hurt me but I guess I’m the only one to see it that way. If I have been horrible, I am forever sorry and I’m now getting what I deserve.”