She doesn’t know her son is suspected of murder, at this point. She just thinks he has been passing bad cheques again.

“That gun cost over a hundred dollars. Dick bought it on credit, and now the store won’t have it back, even though it’s not hardly a month old and only been used the one time–the start of November, when him and David when to Grinnell on a pheasant shoot. He used our names to buy it–his daddy let him–so here we are, liable for the payments, and when you think of Walter, sick as he is, and all the things we need, all we do without …” She held her breath, as though trying to halt an attack of hiccups. “Are you sure you won’t have a cup of coffee, Mr. Nye? It’s no trouble.”

Truman Capote, In Cold Blood, p. 171

Just look at that masterful dialog, how it breaks your heart!