WASHINGTON -- Republican Sen. Thom Tillis of North Carolina says he was "overheated" during a Washington, D.C., race Wednesday morning, in which he collapsed and was taken away by ambulance.

Tillis, 57, was seen on the ground at about the two-mile mark in the three-mile race in Anacostia Park in the southeast part of the city.

Tillis at first appeared unconscious but was revived and breathing when taken away by ambulance from the ACLI Capital Challenge Three Mile Team Race.

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In a video posted to Twitter later Wednesday morning, Tillis said he's "fine" and said doctors were "just checking me out."

I'm doing well. Looking forward to getting back to work. Thanks for all of your prayers and well wishes. #CapChallenge pic.twitter.com/uQGQp85qzR — Senator Thom Tillis (@SenThomTillis) May 17, 2017

Tillis was participating in the ACLI Capital Challenge race, an annual event in Anacostia Park in the district. He was leading his own team, "Team Tillis."

Many politicians and other prominent Washington, D.C., figures run the annual race. Proceeds go to charity.

Tillis' Senate colleagues immediately called for prayers for the North Carolina senator.

Tillis is the junior North Carolina senator, elected to the Senate in November 2014 after serving in the North Carolina legislature from 2009-2015. He serves on the Senate Armed Services, Judiciary, Veterans Affairs and Banking, Housing and Urban Affairs committees, as well as the Senate's Special Committee on Aging.