Using both a question mark and an exclamation point, while not as bad as a frakkin’ interrobang, is still ugly. If you want to give a question extra emphasis, you italicize that thing. Then the question mark is the only end punctuation you need. (Yes, I know interrobangs are normal in some languages. You’re here to improve your knowledge of written English, are you not?) The argument that writers should avoid all uses of italics because ‘italics stand out too much and make the reader aware that they’re reading’ is a sorry-ass excuse for double-stacking the end punctuation instead. That stands out a lot more than italics, believe me.
Hyphenate all of twelve-year-old, not just part of it.
“And why do we have to bring a twelve-year-old to a crime scene?”
The boy smiled faintly and replied, “Detective, I am here for your protection.”
If you want to avoid using italics for a full sentence, I recommend something like this instead: “And why do we have to bring a twelve-year-old to a crime scene?” he shouted.