The alleged perpetrator was captured on Monday hours after the bodies of the victims were discovered in Godoy Cruz.
The alleged perpetrator was captured on Monday in the western Argentina province capital of Mendoza hours after the bodies of the victims were discovered in the neighbouring town of Godoy Cruz.
The suspect stabbed to death his partner, her sister and their 80-year-old mother, while he also left his 7-month-old child with life-threatening injuries.
According to Mendoza security minister Gianni Venier, an 11-year-old son of the couple was also injured in the attack but managed to hide and call the police.
On Wednesday women numbering in the tens of thousands marched in the streets of many Argentinean cities to protest the ongoing outbreak of violence against women.
Report says in 2015 there were 286 so-called femicides in the country.