[RJ]

re: He behaved like a petulant child..

Adj. 1. petulant - easily irritated or annoyed; "an incorrigibly fractious young man"; "not the least nettlesome of his countrymen"
irritable, peevish, pettish, techy, testy, tetchy, scratchy, nettlesome, peckish, cranky, fractious; ill-natured - having an irritable and unpleasant disposition, sulky, cross, moody, sour, crabbed, impatient, pouting, perverse, irritable, crusty, sullen, bad-tempered, ratty Brit., N.Z. (informal) fretful, waspish, querulous, peevish, ungracious, cavilling, huffy, fault-finding, snappish, ill-humoured, captious ..OPPOSITE good-natured