A five-year-old boy was shot dead by his mother in a tragic murder-suicide earlier this month and now the boy's father is speaking out about how he warned authorities about his mentally ill ex-wife.

Kenny Kreuscher was visiting family in Montana on March 5 when his mother, 41-year-old Sara Atkinson, shot him in the head in his sleep before turning the gun on herself.

The boy's father, Ken Kreuscher, says that he had been trying to gain full custody of his son for years, after watching his wife become more and more mentally unstable.

Still, he says that Denver Child Protective Services failed to heed his warnings and are responsible for the boy's tragic death just days before his sixth birthday.

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Five-year-old Kenny Kreuscher (right) was visiting family in Montana on March 5 when he was shot dead by his mother, 41-year-old Sara Atkinson (left), in his sleep.

Kreuscher says he broke up with his wife a few years ago, and since then they had shared custody of their son.

The boy's father, Ken Kreuscher (pictured), says he has been warning child protection services about his wife's paranoid behavior for years

Recently, Kreuscher says his ex had stopped taking medications and was becoming increasingly paranoid, believing there were cameras and bombs hidden away in her home.

She also became violent towards their son, Kreuscher claims.

In one video - recorded just days before his son's death - Ken speaks to Kenny about a bruise on his arm allegedly caused by the boy's mother.

'She punched me like that,' Kenny says in the clip.

'Who punched you?' his dad asks.

'Mommy,' the boy responds.

Kreuscher says he showed the video to a case worker, who came to visit his home shortly after. However, the case worker reportedly told the concerned father that there wasn't much she could do.

'And she stood in front of me and pointed at my closet and said, "Unless your kid's being stuck in a closet every day or beaten every day, I'm not going to do anything about it, and if you call back, if I hear back from you about this kind of stuff, I'm going to take him from you and her,"' Kreuscher told KDVR.

Kreuscher says he tried in vain to get a restraining order against his ex and that she even threatened to kill their son before.

'She had threatened to do it before,' Kreuscher told KUSA. 'She said, "I'm going to kill myself. I'm going to take him with me."'

In one video - recorded just days before his son's death - Ken speaks to Kenny about a bruise on his arm allegedly caused by the boy's mother

Denver child protection authorities released a statement following the boy's death, adding that they can't release many details on the situation as of now.

'The loss of this child is an absolute tragedy for this family, their loved ones and friends, and for our community and agency. We are working to understand the circumstances surrounding this horrible act,' the statement reads.

Kreuscher says he is speaking out in an attempt to stop a similar tragedy from happening to another parent.

'I'm here because I don't want this to happen to anybody else. It's not right what they did,' he said.

A memorial was held for Kenny on Sunday. He would have turned six years old on Saturday.