Shocking / The 5-month-old baby dies suddenly, her mother's boyfriend is arrested, what happened the night before the serious act in their house is revealed (PHOTO)

A serious incident occurred in South Yorkshire, England where a 5-month-old baby died in mysterious circumstances.

It was initially reported that the little girl suffered cardiac arrest, but then police launched an investigation into a 24-year-old man who is suspected of having strangled her.

He is learned to be the person with whom his mother cohabited while the true cause of death is still unknown. Preliminarily it is said that the couple had a quarrel the night before the baby's death.

Her mother, who remained anonymous, desperately reveals that the little girl with sky-blue eyes had changed her life.

"From the day she was born, I always called her beautiful, she always just smiled," she said.