Please advise: my cat killed one of the parents of tit family nesting in our garden. the chikes are a couple of weeks old.

Hello community,

Our day started very bad.
We have a birdhouse in the garden and a pair of Tit birds have formed a nest and the chicks hatched about 2-3 weeks ago.
It was so beautiful to see every morning both parents going back and forth with worms to feed the chicks.

This morning though we had a very bad surprise when our cat brought in a badly injured Tit bird. despite all our efforts to save it, it died within the hour. 

Now (2 hours after) we see the other parent looking for the missing spouse all over and because of that, the chicks aren't getting fed.

Will the remaining parent stay with the chicks or will it abandon them?
If he abandons them, What should we do to save them?

Thank you!

For the cat, he is under house arrest until the chicks fly off the nest. We should have done it earlier.