burst out into something
and burst into something 1. Fig. [for plants or trees] to open their flowers seemingly suddenly and simultaneously. (Burst indicates suddenness.) The flowers burst out into blossom very early. They burst into blossom during the first warm day.
2. Fig. [for someone] to begin suddenly doing a particular activity, such as crying, laughing, chattering; to begin an activity such as laughter, chatter, tears, etc. Suddenly, she burst out into laughter. The child burst into tears.