to fly into a rage; to lose one's temper; to flare up; to break out
彼女は突然怒り出した。
She suddenly flew into a rage.
部長は数字を見て怒り出して席を立った。
The manager looked at the numbers, flew into a rage, and stood up.
小さな誤解で突然怒り出す客もいる。
There are also customers who suddenly fly into a rage over a small misunderstanding.