Michael James Riddering was one of 28 people killed after terrorists opened fire
Friday night at a cafe in the capital, Ouagadougou.
The al Qaeda-linked militants then raided a luxury hotel across the street, shooting some and taking others hostage in an overnight siege that lasted hours.
Sheltering Wings, a missionary group that supports Riddering's orphanage, provided a detailed account of his ordeal.
It said the Florida resident and his wife, Amy Riddering, worked at the orphanage in Yako, 115 kilometers (70 miles) from the capital.
Riddering, 45, was in Ouagadougou to pick up a team of missionaries visiting from the United States and stopped by Cappuccino cafe with a friend, the group said.
Attackers stormed in and started shooting. The friend, identified only as Pastor Valentin, hastily called Riddering's wife and told her they "urgently" needed prayers. Then the phone went dead.
"It appears that Pastor Valentin was somehow separated from Mike during the attack and hid somewhere in the Cappuccino cafe," the missionary group said.
Riddering's body was found in a morgue later. The pastor was rescued by security forces.
'Best friend, partner in crime'
In a Facebook post, Amy Riddering said the pastor called
using her husband's phone.
"Heaven has gained a warrior! I know God has a purpose in all things but sometimes it is a complete mystery to me," she posted.
"My best friend, partner in crime and love of my life. The best husband ever. ... My heart is so heavy and I am having trouble believing he is gone."
Amy and Michael Riddering moved to the West African nation five years ago from Hollywood, Florida. Before that, he owned a boat company in his home state.
The parents of four adopted two children in Burkina Faso, according to the missionary group.
"The Ridderings and their team care for about 400 orphaned children (and) provide direct assistance to disenfranchised widows," Sheltering Wings said.
U.S. State Department spokesman John Kirby sent his condolences to the family.
"Our thoughts and prayers are with his family at this difficult time, as they are with all those affected by this brutality," he said.
Others killed in the terror attack included French, Canadian and Ukrainian nationals.