Jovenel Moïse, gunned down in front of his family this week, made many enemies and few friends in four scandal-plagued years as president of Haiti.

So many enemies that when a squad of mercenaries posing as agents from the US Drug Enforcement Administration (DEA) stormed the president’s private villa in the early hours of Wednesday, it was not entirely clear which side his bodyguards were on. Haitian authorities have since ordered the interrogation of his security detail.

Video shot by witnesses circulating on the internet appear to show the killers closing in on the house under cover of darkness in a slow-moving convoy of vehicles. Some of the attackers walk between the cars brandishing submachine guns and shout in English “DEA operation” and “do not shoot”.

Once inside, the assassins fired repeatedly at Moïse and his wife Martine. The president was hit 12 times and his left eye was gouged, investigating magistrate Carl Henry Destin told Le Nouvelliste, a Haitian newspaper. Martine survived the attack with serious injuries and was airlifted to Florida for treatment.

The attack prompted international condemnation and in Haiti, consternation despite the country’s endemic violence. “People are in limbo right now,” said one resident of Port-au-Prince. “Whether you loved Moïse or hated him, it’s the same reaction: a deep state of shock.”

Among the many unanswered questions are: who ordered the killing, why the bodyguards apparently offered no resistance and what will happen next in Haiti, already in deep crisis even before the assassination.

White House press secretary Jen Psaki on Friday said US FBI and homeland security officials would be dispatched to Port au Prince “as soon as possible to assess the situation and how we may be able to assist” at the Haitian government’s request.

Although murders are common in the Caribbean nation and coups punctuate Haiti’s history, no president has been assassinated in office since a mob dismembered Jean Vilbrun Guillaume Sam in 1915.

That killing prompted a 19-year occupation of Haiti by US troops but Washington’s reaction this time was different. Psaki on Thursday said presidential elections scheduled for this year should proceed.

In Haiti, the authorities have been quick to highlight the foreign identities of the president’s killers. Police chief Leon Charles on Thursday said that 26 of the 28-man hit squad were Colombian and two were Americans of Haitian descent. Seventeen have been arrested and at least three killed. Others are on the run. It is unclear why the supposedly professional hit squad failed to organise a getaway.

Speculation is rife as to who ordered the assassination. Moïse, a former banana exporter, had shown an increasingly authoritarian streak in his final period in office, jailing opponents, ruling by decree, allowing the terms of parliamentarians and mayors to expire without fresh elections and seeking constitutional changes that would have abolished the senate, given him immunity from prosecution and cleared the way for a second term.

Violent street protests erupted in 2018 over accusations that Moïse and his officials had pocketed millions from a Venezuelan subsidised oil scheme, something he always denied.

“Moïse had a large number of enemies,” said Laurent Dubois, a Haiti expert at the University of Virginia. “One could speculate in many different directions. I imagine this will be traced back to an internal source but it’s hard to say whether we’ll ever really know.”

Equally murky is what comes next in a country wracked by political instability, worsening gang violence and acute poverty. Claude Joseph, Moïse’s sixth prime minister, moved swiftly to assert control after the killing, imposing a state of emergency, holding a news conference and ordering the airport and local businesses to reopen after two days in which the streets had been quiet. However, Ariel Henry, a neurosurgeon nominated by Moïse two days before his death to take over as premier, claimed he was the legitimate leader.

Constitutional experts were foxed: Haiti has two possible legal formulas in the event of a presidential death, there is currently no sitting parliament to endorse a nominee and the head of the supreme court — a possible successor — died of coronavirus last month.

For now, the US and the United Nations are dealing with Joseph; secretary of state Antony Blinken spoke to him on Wednesday and State spokesperson Ned Price repeatedly described Joseph as “the acting prime minister”.

Whoever takes over faces a steep challenge. In April, the Catholic church warned that Haiti was “descending into hell” after seven of its clergy were kidnapped and observers said there had been a marked deterioration in security from early June as gang violence surged.

“We need this government which has no legitimacy to accept a process of dialogue with all those who could constitute a national unity government,” said Didier Le Bret, who served as France’s ambassador to Haiti from 2009-13 and now works for a consultancy, ESL & Network. “No electoral process is possible in Haiti for months because none of the conditions can be met.”

Even before the killing, Bruno Maes, Unicef country representative, said Haiti was facing its worst humanitarian crisis in years because of violence by armed groups, acute fuel and food shortages and an upsurge in Covid cases. “The number of people who need immediate humanitarian assistance is 1.1m,” he said. “We cannot use the main road to the south to reach people because armed gangs are controlling it so we have to use helicopters.”

International powers seem unwilling to intervene. A 13-year UN mission to Haiti ended in 2017 without bringing lasting stability and critics said a Security Council statement this week amounted to little more than hand-wringing. With the US, the traditional arbiter, on the sidelines, some fear Haiti risks drifting into violent anarchy.

“The poor people of Haiti have suffered enough,” said one local businessman. “People are dying, people are hungry. The people can’t take it any more. Life is too painful.”