Take somebody by surprise
Definition 1 of 1
Pro Tip 1/3Sudden Reveal
The phrase implies an unexpected disclosure that causes shock or surprise. 
The CEO’s resignation took the company by surprise.
Pro Tip 2/3Emotional Impact
It can highlight a strong emotional response, not just mild astonishment. 
The news of the accident took her by surprise, leaving her speechless.
Pro Tip 3/3No Anticipation
Used when something happens without any warning or expectation. 
An early spring snowstorm took the farmers by surprise.