Mrs Krim also found her two children in the bathtub with stab wounds covering their bodies, and then tried to stop the nanny's neck from bleeding with a towel, according to the Post.
Neighbours said she then ran outside the apartment and collapsed by its front door.
Rima Starr, 63, said: 'I heard blood curdling screams and I went down to the lobby and there was the mother screaming blood, hunched over the three year old and swaying with the three year old.
'At time she was screaming things like: 'I'll never speak to her again', repeating that over and over again, then 'it's all right, you'll be all right, you'll be alright' to the child.
'Then she would get waves of the reality of what just happened an then she'd go into just plain bloodcurdling screams with her arms flailing out to the sides.'
One neighbour revealed the superintendent of the apartment block went into the apartment and questioned Ortega, demanding: 'So you cut her throat? So you stabbed her in the neck?'
His wife then came out to assist and told horrified neighbours who had heard the screams: 'Two babies, in the bath, nanny' and made a cutting sign across her throat.
Mrs Friedman added: 'At that point I knew the nanny had something to do with it'.
Neighbours dialed 911 and, although Lulu and Leo reportedly appeared to be breathing when medics arrived, they were pronounced dead on arrival at hospital.