Kimberly, 49, a neonatal intensive care nurse, and James Snead, 48, a military intelligence analyst, agreed to allow the 19-year-old live in their Parkland home after their son, a friend to Cruz, inquired.
Cruz's new home at the Snead residence came just days after his adoptive mother, Lynda Cruz, passed away from pneumonia on November 1.
The Snead couple have now revealed that they failed to see the dark side of Cruz, who gunned down 17 innocent individuals in a Valentine's Day rage.
While speaking with the South Florida Sun Sentinel, a wearied Kimberly said: 'We had this monster living under our roof and we didn't know.'
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In this Feb. 17, 2018 photo, James Snead and his wife Kimberly appear at an interview about the shooting at Marjory Stonemason Douglas High in Parkland, Florida, where 17 people were killed
The Sneads recounted their time living with the shooter, Nikolas Cruz. The couple said they didn't see his dark side
Kimberly and James said Cruz lived with them for only three months. They took him in after his mother died
This booking photo obtained February 15, 2018 courtesy of the Broward County Sheriff's Office shows shooting suspect Nikolas Cruz
Pictured above is the Snead's Parkland home where Cruz lived for just three months before he shot dead 17 people at his high school in a Valentine's massacre
Her husband, James, also added: 'Everything everybody seems to know, we didn't know... It's as simple as that.'
The couple told the local newspaper in a sit-down interview they knew Cruz had been 'extremely depressed' after the death of his last living guardian, Lynda.
They said he was noticeably 'immature' but seemed to be 'growing happier' after moving into a new home.
Cruz had unusual eating habits and at times would place cookies inside steak and cheese sandwiches.
The family, who had pets in their home - claimed there were no signs of animal cruelty - despite several claims by neighbors who revealed disturbing details about Cruz's treatment toward animals.
Pictured: Cruz as a baby with his adoptive mother, Lynda Cruz. Lynda died from pneumonia on November 1 before her son moved in with the new family
The Snead couple (shown) claims the night prior to the Valentine's Day shooting, there was no indication Cruz had unusual behavior
The couple admitted they allowed the 'gun-obsessed' teen to keep an AR-15 rifle in their home, however, as they are avid about gun safety, they made him buy a locking safe to keep in his bedroom.
Inside the safe, were other various guns as well as knives. The pair instructed Cruz to ask for permission before unlocking the safe - which they claimed to the Sentinel he did twice since moving in.
Kimberly reportedly encouraged Cruz to attend therapy sessions after the passing of his adoptive mother.
She said just five days before the shooting, she and Cruz attended a session together.
Still, the couple claims the night prior to the Valentine's Day shooting, there was no indication the teen had any unusual behavior.
'We had this monster living under our roof and we didn't know,' Kimberly said of Cruz
The parents reportedly asked Cruz if he needed a ride to school the morning of February 14, when he declined and said he didn't even need to go.
'It's Valentine's Day and I don't go to school on Valentine's Day,' he said, the couple told the Sentinel.
The Sneads recalled receiving the 'panic-stricken' phone call from Cruz around 2.30pm that day.
Cruz informed them about a shooting at Marjory Stoneman Douglas High - when James told him to walk to the nearby Walmart and that he was on his way to pick him up.
During the drive, James received a troubling phone call from a SWAT officer inquiring about Cruz's whereabouts.
The expelled 'gun-obsessed' student was taken into custody by the time the Sneads saw him on February 14
That's when James realized there were more troubling details to the story.
James phoned the officer back and ordered police to rush to their Parkland home to check on his wife.
'I need a police presence at my house. Go make sure my wife is OK,' James urged in the phone call.
'I was fearing for her life,' he recalled in the interview.
Shortly after, Kimberly answered the door, when officers ordered her to put her 'hands up'.
Cruz (shown Thursday at his first court appearance) is facing 17 charges of premeditated murder for the mass shooting at Marjory Stoneman Douglas High School
Police raided the home while Kimberly feared the worst.
Cruz was taken into custody by the time Kimberly and James saw him for the first time since the massacre.
James told the Sentinel that he was forced to hold Kimberly back when she attempted to charge after Cruz while in custody. In a panic, Kimberly then told Cruz: 'Really, Nik? Really?'
James added: 'He said he was sorry... he apologized. He looked lost, absolutely lost.
'That was the last time we saw him.'
Despite the couple's claims they didn't notice his disturbing behavior, the teen was expelled from school last year, while neighbors and friends revealed details of his love for violence and weapons.
Police had been called to Cruz's homes as many as 39 times over the course of seven years over reports of violence or suspicious behavior.