40-year-old Domingo Villa Arellano , who is an ex-cop , allegedly carried out the slayings on March 15 inside Puente Grande prison . Villa Arellano admitted to stabbing his girlfriend Ericka Isela Velazquez Cocula 's chest with a weapon during a verbal dispute . Villa Arellano was furious over the couple 's three children saying their mother was treating them poorly . He went after the children and his girlfriend 's 17-year-old daughter .
40-year-old Domingo Villa Arellano , who is an ex-cop , allegedly carried out the slayings on March 15 inside Puente Grande prison . Villa Arellano admitted to stabbing his girlfriend Ericka Isela Velazquez Cocula 's chest with a weapon during a verbal dispute . Villa Arellano was furious over the couple 's two children saying their mother was treating them poorly . He went after the children and his girlfriend 's 17-year-old daughter .