Wilson Joseph, who runs the 400 Mawozo gang that police say is holding 17 members of the missionary group, made the violent threat in a new video released on social media.
“I swear by thunder that if I don’t get what I’m asking for, I will put a bullet in the heads of these Americans,” he said, according to The Associated Press.
The gang has demanded $1m per person after it abducted 16 Americans and one Canadian, including five children, and their driver.
Joseph also threatened the impoverished Caribbean country’s Prime Minister Ariel Henry and Léon Charles, the chief of Haiti’s National Police.
“You guys make me cry. I cry water. But I’m going to make you guys cry blood,” he said in the video, which was shot in front of coffins that seemingly contained the bodies of recently killed gang members.
The missionaries are associated with the Ohio-based Christian Aid Ministries, which has said the group is made up of five men, seven women and five children.
The adults are aged between 18 and 48, while the five abducted children include an 8-month-old baby and youngsters ages 3, 6, 13 and 15 years old.
Among the kidnapped are members of a family from the congregation of Dunkard Brethren Church in Hart, Michigan, according to the church officials.
The family, who have not been named, had arrived in Haiti earlier this month and were expected to stay several more months, the church’s minister Ron Marks told CNN.
The group was kidnaped on Saturday after they visited an orphanage in Croix-des-Bouquets, a northeast suburb of the capital Port-au-Prince.
It is the latest in a string of kidnappings in the country, which has been rocked natural disasters, poverty, political instability and civil unrest.
The FBI has agents on the ground who have been helping local officials with the investigation.
The non-profit Center for Analysis and Research for Human Rights says that 400 Mawozo has abducted dozens of people this year, including foreigners.
CARDH says that there has been 628 kidnappings since January, involving 29 foreigners, with an increase of nearly 300 per cent since July.