Buchanan, 57, had recently contracted the delta variant and was battling the virus in the ICU.
It happened after Buchanan returned from a trip to Kentucky in late July.
"He got back on Saturday, July 25. So shortly after that flight, he felt bad and he developed a fever," his best friend Natalie Henshilwood told ABC13. "He tested positive for COVID on July 30. He was admitted to the hospital on August 4 with the delta variant."
She said Buchanan got the Johnson & Johnson vaccine, but he had underlying conditions, including high blood pressure.
"He was pre-diabetic and he was on medications for both," said Henshilwood earlier this week.
Buchanan was intubated and on dialysis.
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He was well-known in the pageant circuit and worked for an airline, drove for Uber, and worked as a real estate agent.
While Buchanan had the vaccine, more than 90% of hospitalized patients are not vaccinated.
Buchanan's husband, Osmar, contracted the virus, too, but did not end up in the hospital. He had a mild case.
Henshilwood created a GoFundMe to give back to others in honor of her friend, a man who has touched so many lives.
According to his GoFundMe page, Buchanan wanted to live so he could plan a trip to Disney with all of his friends.
A candlelight vigil was set to be held in his honor Friday night in the parking lot of HCA Houston Healthcare in Kingwood. The vigil was scheduled for 8 p.m., with a novena, or form of prayer, following right after.
The video above is from Marla Carter's report earlier this week on Buchanan's COVID battle.
For updates on this report, follow ABC13 reporter Marla Carter on Facebook,Twitter and Instagram.