Story highlights Iowa Libertarian Senate candidate Doug Butzier dies in a plane crash Monday

He was a medical doctor at Mercy Medical Center-Dubuque

The cause of the crash is still unknown

Butzier's name will remain on the ballot in the November election

A medical doctor-turned Libertarian Senate candidate in Iowa died when a plane he was piloting crashed around 11 p.m. Monday.

Doug Butzier, 59, was earning less than 2% of the vote in the competitive statewide race between Democratic Rep. Bruce Braley and Republican state Sen. Joni Ernst to replace retiring veteran Sen. Tom Harkin.

"He was a leader among his peers," said Russell Knight , the president of Mercy Medical Center-Dubuque, the hospital where Butzier worked. "We will all miss his strong, intelligent, thoughtful presence, and we express our collective condolences to Doug's family, friends, and colleagues."

Butzier was a practicing emergency medicine doctor and president of the medical staff at the hospital, according to his campaign website.

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Information about the cause of the crash has not been publicly released, although the National Transportation Safety Board and the Federal Aviation Administration will investigate.

The plane failed in its first approach to land on the runway, and it crashed the second time, according to a local news report . It remains unclear if weather played a role in the crash, although it was raining during the day and into the night Monday.

Because the deadline for changing candidates has passed, Butzier's name will still appear on ballots in Iowa next month. Both Braley and Ernst released statements expressing condolences to Butzier's friends and family. He is survived by his wife and two sons.