A suicidal Florida woman is accused of fatally stabbing her two-year-old son before turning on her boyfriend and herself, police said.

Nathaly Ramos, 22, allegedly stabbed her son Alphonse to death in their South Miami-Dade home. Jail records reveal Ramos was charged with second-degree murder and attempted second-degree murder after stabbing herself and her boyfriend.

Police did not reveal the motive behind the stabbing but said a suicidal woman stabbed her son to death, wounded a man and later turned the weapon on herself on Sunday (4 February).

According to The Miami Herald, Ramos was taken to Homestead Hospital in a critical condition Sunday night.

Ramos' boyfriend told police he was awakened by pain to his body and his girlfriend holding a knife and stun gun.

He claimed Ramos chased him but he managed to lock himself in a bathroom. The man, who was not identified, was taken to Jackson South Community Hospital.

Neighbours revealed Ramos lived with her mother and her other children in a government housing complex near Homestead. She was described as a depressed and troubled young woman who did not have custody of her child and lived in a shelter.

"Even before she had the baby she was always an emotional wreck," a neighbour, who asked to remain unnamed, said.

Police took Ramos into custody on Sunday at around 4pm. The Miami Herald reported that Miami-Dade police did not confirm Ramos' identity or release any information on the stabbing. She is being held without bond.