A pregnant woman and her husband and child were on Sunday killed by members of the dreaded Badoo group in Ikorodu area of Lagos State.
Only the girl child in the family survived the attack of the Badoo boys.
It was gathered that the stomach of the woman was slit open and her foetus removed.
Those killed were Israel Olusanya 45; Rukayat Olusanya 39; and Joseph Olusanya.
The girl who survived was identified as Esther Olusanya.
Four of those believed to have carried out the attack were, however, arrested by members of the Neighbourhood Watch.
But following the beating they received after they were apprehended, the Badoo boys were said to have bled to death.
The spokesman of the Lagos State Police Command, Olarinde Famous-Cole, confirmed the development.
Famous-Cole said the command has launched investigation into the incident and would soon apprehend others involved in the dastardly killing.