Never use an adverb to modify the verb 'said' . . . he admonished gravely. To use an adverb this way (or almost any way) is a mortal sin. The writer is now exposing himself in earnest, using a word that distracts and can interrupt the rhythm of the exchange.
Elmore LeonardThere are 500 million people on Facebook, but what are they saying to each other? Not much.
Elmore LeonardI still read Hemingway. I still read his short stories because they're so good. He doesn't waste any words.
Elmore Leonard