A supposedly playful activity by an eight-year-old autistic child left his mother terrified after she found horror-style messages written all over her son's bedroom walls. Some of the messages read "you will die" and "I'm going to kill you".

Initially, Kayleigh Parnham, from Maidstone, Kent, did not know who had scribbled the creepy messages. But upon investigation, she realised that it was none other than her son Alex.

The 30-year-old mother said she checked the room's walls with a UV pen and discovered more strange writings written over them that included similar messages like "ssh..." and "you will die".

Parnham, who works as a teacher, said that she got to know about the horror-style scribblings after her seven-year-old daughter Ellie alerted her.

"I bet we look like a bunch of psychopaths," she said after she found the scary messages.

"I couldn't believe when I discovered my darling son had done that. When I first found it, I was a bit in shock, to be honest. The little darling then showed me another message he'd written that said his little sister was going to kill everyone.

"Luckily, he'd also written 'I love you' on his sister's bed, so he's not a complete demon," the mother-of-three was quoted as saying by the Mirror.

Parnham said that instead of scolding Alex, she confronted him and asked him the reason for his "disturbing" activity. The little boy said that he thought it would be fun because the notes could only be seen under UV light.

The young mother added that her son loves to watch the Ninjago ghost episode – he loves Ninjago – as they killed the "baddies" in it. His messages were allegedly inspired by the fight scenes from Lego Ninjago and the Spiderman films.

Parnham further explained, "I'm a strict parent, I never let the kids watch films or play games that are too old for their age like some parents do. He's autistic, so his mind doesn't work the same way as other people. In his mind, it was fine because he'd written it in invisible ink. I couldn't really argue with that logic."

She added that she had sent a video of the messages to her friends to get their advice.

"We had to sit down together as a family and discuss the rules of writing on walls again – even if it is with invisible ink," the mother said.

Parnham also posted a video on Facebook, writing, "The moment you discover your child is a creepy demon spawn with homicidal tendencies..."