He can't even realize the seriousness of what he did!
In autumn he gave himself up to hunting with the same business-like seriousness--leaving home for a month, or even two, with his hunt.
But then the seriousness of the matter began to sink in.
In his later years he overcame the drunkenness that was habitual to him in youth; he developed seriousness of character and unselfish devotion to what lie believed was the cause of patriotism; and he won the respect of men of high character and capacity in France and Holland.
In spite of the seriousness of the situation, Dean was forced to stifle a chuckle.