The attack took place around 1:00 am (0500 GMT) at Moise’s home. Shell casings could be seen on the street outside as forensics experts combed the scene for evidence, and a nearby car was peppered with bullet holes with one window shattered.
Moise’s wife was first treated at a local hospital then rushed by air ambulance to the Ryder Trauma Center in Miami.
Joseph said she was “out of danger”, later adding that “her situation is stable.”
He said the president was “assassinated at his home by foreigners who spoke English and Spanish.”
“This death will not go unpunished,” Joseph said in an address to the nation.
Haiti’s ambassador to Washington, Bocchit Edmond, said the killers were “professional” mercenaries disguised as US Drug Enforcement Administration agents.
“We have a video and we believe that those are mercenaries,” he said.
Moise had ruled Haiti, the poorest country in the Americas, by decree after legislative elections due in 2018 were delayed.
In addition to the political chaos, kidnappings for ransom have surged in recent months, reflecting the growing influence of armed gangs in the country.
Haiti also faces chronic poverty and recurrent natural disasters.
The capital’s streets were at a standstill in the hours after the assassination, with just a handful of citizens who expressed fear and disbelief.
“We didn’t expect it. This is another earthquake in Haiti,” said a mother of two who gave her name only as Bernadette, referring to the disaster which devastated the country in 2010.
“I can’t believe it, I can’t believe it,” said 50-year-old Jacquelyn.
The country will observe two weeks of national mourning from Thursday.
The president had faced steep opposition from swathes of the population that deemed his mandate illegitimate, and he churned through seven prime ministers in four years.
Joseph—who spoke by telephone to US Secretary of State Antony Blinken Wednesday—has only been in his post for three months, and was due to step down within days after Moise named his replacement on Monday.
As well as presidential, legislative and local elections, Haiti was due to hold a constitutional referendum in September after it was twice postponed due to the coronavirus pandemic.
US president Joe Biden condemned the killing as “horrific” and said Washington was ready to assist in any way.
“We condemn this heinous act, and I am sending my sincere wishes for First Lady Moise’s recovery,” Biden said.
Washington also called for Haiti to proceed with the elections, with State Department spokesman Ned Price saying a fair vote would “facilitate a peaceful transfer of power to a newly elected president.”
UN secretary-general Antonio Guterres called on Haitians to “remain united” and “reject all violence.”
European Union foreign policy chief Josep Borrell warned of “risk of instability and a spiral of violence.”
Governed by decree
Moise—a 53-year-old former entrepreneur from the island’s north—burst onto the political stage in 2017 with a message of rebuilding, campaigned on populist pledges, and was sworn in in February 2017.
The end date of his mandate became the source of a tense standoff.
Moise maintained that his term of office ran until February 7, 2022, but others claimed it ended on February 7, 2021.
The disagreement stems from the fact that Moise was elected in a 2015 vote that was cancelled for fraud, and then re-elected in November 2016.
Without a parliament, the country fell further into crisis in 2020, and led to Moise governing by decree, fuelling growing mistrust of him.
Though calm held in the hours after the assassination, many feared Haiti could tip further into violence.
“How much worse can hell get?” asked Haiti expert Irwin Stotzky, a professor at University of Miami law school.
“Haiti faces even more violence and death and failure as a democratic nation than ever before, which is hard to imagine given its recent and chaotic history.”
The killing comes days after Moise appointed Ariel Henry, a neurosurgeon who studied in France, as Haiti’s new prime minister.
Henry, 71, is close to the opposition, but his appointment was not welcomed by the majority of opposition parties, who had continued to demand the president step down.
The Dominican Republic ordered the immediate closure of its border with neighboring Haiti after the assassination.