The couple were working as missionaries in the capital Port-au-Prince when they were killed leaving a local church.
The daughter and son-in-law of a Republican politician are among three Americans killed by gangs in Haiti.
Davy and Natalie Lloyd, a missionary couple in the country, were shot dead in capital Port-au-Prince after being ambushed as they left a youth group activity held at a local church, according to a police official.
Their identities were confirmed in a Facebook post from Ms Lloyd’s father, Missouri state representative Ben Baker.
A third person, as yet unnamed, was also killed during the attack on Thursday evening in the community of Lizon in northern Port-au-Prince, Lionel Lazarre, head of a Haitian police union, told The Associated Press on Friday.
“My heart is broken in a thousand pieces. I’ve never felt this kind of pain,” Mr Baker wrote.
“Most of you know my daughter and son-in-law Davy and Natalie Lloyd are full time missionaries in Haiti.
“They were attacked by gangs this evening and were both killed. They went to Heaven together.
“Please pray for my family we desperately need strength. And please pray for the Lloyd family as well. I have no other words for now.”
The couple worked for Missions in Haiti Inc, an Oklahoma-based organisation founded by Mr Lloyd’s parents.
Ms Lloyd’s social media posts indicated the couple married on 18 June 2022, and she began working with the missionary organisation in August of that year.
She frequently posted photos of Haitian children on her Facebook page.