A firefighter from the Glendale Fire Department rings a bell during the 9/11 Tower Challenge Sept. 11, 2019, at the Gila River Arena, Glendale, Ariz. Participants rang a bell signifying their completion of the 2,071 steps they climbed during the challenge. The steps represented the 110 floors of the World Trade Center first responders climbed during the terrorist attacks that occurred Sept. 11, 2001.
 

Luke Air Force Base Honor Guardsmen present the colors during the 9/11 Tower Challenge Sept. 11, 2019, at the Gila River Arena, Glendale, Ariz. Military members, emergency responders and community members climbed more than 2,000 steps to honor those who lost their life during the 9/11 terrorist attacks.
 

Brig. Gen. Todd Canterbury, front left, 56th Fighter Wing commander, along with military and local community members watch a video during the 9/11 Tower Challenge Sept. 11, 2019, at the Gila River Arena, Glendale, Ariz. During the 9/11 Tower Challenge community members honored the men and women who lost their life during the 9/11 attacks against the United States.
 

Tech. Sgt. Tyler Hendrix, 56th Security Forces Squadron kennel master, carries a military working dog during the 9/11 Tower Challenge Sept. 11, 2019, at the Gila River Arena, Glendale, Ariz. Military members, emergency responders and community members climbed more than 2,000 steps to honor those who lost their life during the 9/11 terrorist attacks.
 

A firefighter from the Casa Grande Fire Department climbs stairs during the 9/11 Tower Challenge Sept. 11, 2019, at the Gila River Arena, Glendale, Ariz. Participants climbed 2,071 steps to represent the 110 floors of the World Trade Center that first responders climbed during the terrorist attacks that occurred Sept. 11, 2001.