Passage: On April 19, thousands of students marched from Korea University to the Blue House, and as they marched past other high schools and universities, their numbers grew to over 100,000. Arriving at the Blue House, the protesters called for Rhee's resignation. Police opened fire on protestors killing approximately 180 and wounding thousands. That day the Rhee government proclaimed martial law in order to suppress the demonstrations.On April 25, professors joined students and citizens in large-scale protests outnumbering soldiers and police who refused to attack the protestors.

Question: How many protesters were killed?
180