panic (one) by (doing something)
To do something that causes one to experience an extreme or debilitating amount of fear or anxiety. Forecasters panicked millions of people by incorrectly predicting the path of the hurricane. I think you panicked him by bursting out the door like that.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
panic someone by something
to make someone lose control by doing something. She panicked Denise by describing the event too vividly. She panicked her horse by jerking the reins too tightly.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.