Sensitivity to the Cries of a Baby

I was at the Jewish library and was faced with the following situation.  A frum, refined looking young mother was there with a few young children, including a baby.  At some point, the baby - about 4 months old - began to scream.  He screamed and screamed and only paused momentarily before he began screaming again.  The mother held him and looked at books and he screamed. 

One issue was, a screaming baby doesn't belong in a library.  Another issue was THE SCREAMING BABY who, I suppose, was starving.  She did not give him a bottle or pacifier which led me to think he was a nursing baby whom she was going to feed when she got home.  But she was in no hurry. 

I didn't want to say anything to embarrass her but felt that SOMETHING must be said.  I tried to say, "Is that a hungry baby?" but suppose I didn't say it loud enough since the mother kept looking at the book.  With a screaming baby next to her ears, how could she hear me?

I didn't say it louder and closer to her because I was not sure I wanted to say it at all, being afraid to 'start up' with her, but I felt it was wrong for me to keep ignoring the situation.  The librarian didn't say a word.

This went on for about twenty minutes.  The mother was checking out her books and had her little daughter sit and hold the baby, who was screaming.  On and on.  I was very upset at that point and finally said to the mother, "I don't want to say anything, but ... have rachmanus!" (on me, as much as the baby).

She went to her daughter and took the baby, finished checking out and left. 

If I had the opportunity to do it over again, I still don't know what I should have done.  I think the least offensive thing to do would be to say, "Excuse me, it's a library.  I'm sorry, but you'll have to take him out."  That doesn't cast aspersions on her mothering, it's just library etiquette.

Here is the odd postscript.  When I got home, I continued reading an old (2010) magazine that I had started months ago, and came across the following line in the first article I read in which a woman quotes her mother as saying, "A mother will have to give a din v'cheshbon for every minute that her infant cries from hunger."

Was the baby in the library hungry? Had he just been fed before they came to the library? Was he crying for some other reason like colic and this was his fussy time of the day? I don't know.  But this baby was screaming, and although he was being held, it seemed he wasn't being responded to.