He's always been an 'impetuous' young man.
an 'impetuous' decision
(..) There are two drops on your ear infact. India blue is near impossible to wash off. Anyway, rather impetuous of that boy, but you're to experienced to react rashly, which is why the lady for whom you work lent you that necklace. Pearls, diamonds, flawless rubies. (..)2009 Sherlock Holmes