Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: The gunman who killed nine people last week at an Oregon college shot himself in front of his classmates after being wounded by two hero cops. Also revealed on Wednesday was that Umpqua Community College shooter Christopher Harper-Mercer, 26, was discharged from the Army after attempting to commit suicide. Harper-Mercer was discharged after one month of basic training at Fort Jackson, in South Carolina, in 2008. The Wall Street Journal reports that the Army wouldn't disclose details of the 2008 suicide attempt but that it indicates Harper-Mercer was deeply troubled long before he opened fire on his classmates last Thursday.Christopher Harper-Mercer, 26, shot himself in a classroom after being wounded by two hero cops who opened fireHarper-Mercer was discharged from the Army in 2008 for trying to commit suicideTodd Spingath was one of two officers to take down Oregon shooterHis partner and fellow vet, Joe Kaney, was identified earlier this weekThe pair have been hailed for preventing further potential devastationThey rushed into Umpqua Community College five minutes after alert 
 Question:At a Wednesday news conference, authorities said that two police officers in plainclothes were the first to confront Harper-_ after he began shooting at his morning writing class.

Mercer