Haiti's President Jovenel Moïse was assassinated in his private residence in the capital, Port-au-Prince, on 7 July.
Police say a group of mercenaries, most of them Colombians, was behind the attack which they suspect a Haitian doctor of ordering as part of a plot to become president.
Here is what we know so far.
Mr Moïse, 53, was shot dead inside his 香港集運淘寶 in the Pelerin 5 neighbourhood, in the hills above Port au Prince. Police say the murder happened at 01:00 local time (05:00 GMT) on 7 July.
The president was shot 12 times and had bullet wounds to his forehead and several to his torso.
His left eye had been gouged out and bones in his arm and in his ankle had been broken, according to one of the judges conducting the investigation.
He died at the scene and was found lying on the floor on his back, his shirt soaked in blood.
The First Lady, Martine Moïse, was also shot but survived. She has been airlifted to Florida, in the US, and is said to be in a stable condition.
Who shot him?
Haitian police say a group of mainly foreign mercenaries - 26 Colombians and two Haitian Americans - made up the group that carried out the killing.
They have also arrested a Haitian man whom they suspect of having played a key role in organising the attack.
But both the timeline given by the police for the killing and who may have pulled the trigger have come under question.
Haitian opposition politician Steven Benoit told a local radio station on Friday that he believed Mr Moïse had been killed "by his security agents".
"It is not the Colombians who killed him," he told Magik9 radio on Friday without giving further evidence to bolster his claims.
Colombian newspaper El Tiempo quoted an unnamed source within Haiti as saying the group of 28 had arrived at the private residence between 02:30 and 02:40, long after the time given for the president's assassination.
However, the 02:30 arrival time quoted by El Tiempo seems to contradict reports from neighbours who said they had seen several SUVs and "white, armed men" arriving in the neighbourhood at around 01:00.
An audio recording published on the verified Twitter account of Martine Moïse and attributed to the first lady by government officials describes the moment of the attack.
"In the blink of an eye, the mercenaries entered my house and riddled my husband with bullets."
MESSAGE DE LA PREMIÈRE DAME MARTINE MOISE. pic.twitter.com/cFQW70xTFE— Martine Moïse (@martinejmoise) July 10, 2021
Some in Haiti have questioned whether the woman in the recording is Martine Moïse, arguing that it did not sound like her voice, but Haiti's communication's minister insisted it was.
How did the assailants gain access?
Video footage, not independently verified but thought to have been taken by residents, shows armed men dressed in black arriving in several vehicles.
A man, thought to be a security guard, appears to have been forced to lie face down in the street while another man can be heard shouting in English over a loudspeaker, "DEA [US Drug Enforcement Administration} operation, everybody stay down!"
Haiti's ambassador to the US, Bocchit Edmond, said that while the attackers had disguised themselves as US drug agents, he believed there was "no way" they really were US agents.
Officials say that the ground between the property's gatehouse and the residence was littered with cartridge cases, indicating that multiple shots were fired.
Yet the only people injured by bullets were the president and his wife, a fact which has raised questions about the possible complicity of the president's guards.
One Haitian official, Bed-Ford Claude, said he had told police to "interview all security agents close to President Jovenel Moïse". "If you're in charge of the president's security, where were you?" he asked. "What did you do to avoid this fate for the president?"
The president's two top security officials have been summoned to appear at hearings scheduled for 13 and 14 July.
How did the assailants flee the scene?
The group seems to have met with little or no resistance inside the residence or during their initial getaway.
Two domestic staff where tied up and the presidential couple's adult daughter, Jomarlie Moïse, hid in her brother's bedroom and was unhurt. She and her two brothers - who were not in the residence at the time of the attack - are in "safe locations", according to officials.
The timeline immediately after the assassination is not very clear.
Haiti's police chief announced some 24 hours after Mr Moïse's assassination that a fierce gun battle was under way in the Pelerin neighbourhood.
"We blocked [the suspects] en route as they left the scene of the crime. Since then, we have been battling them," said Chief Léon Charles.
Some of the suspects were reportedly tracked down to a house nearby, which was then surrounded by police, and where the gun battle the police chief referred to is believed to have taken place.
A group of 11 fled to Taiwan's diplomatic compound in Port-au-Prince, according to a statement by Taiwanese officials. They were arrested "without problems".
Two suspects who were hiding in a ravine were caught by civilians who had joined in the search.
The body of one alleged gunman was found on the roof of a 香港集運淘寶, where he had bled to death while hiding. Two more suspects were found dead very close to the president's residence.
Who are the suspects?
Haitian police say there are:
- 28 suspects in total, of which
- 20 have been apprehended
- 3 have been killed
- 5 remain at large
Police Chief Charles said 26 of the suspects were Colombian and the other two were Haitian Americans.
An investigating judge said the two Haitian Americans had told interrogators they had been hired as interpreters on the internet.
The two allege that they did not know there was a plan afoot to kill the president, but believed they were to act as interpreters as he was arrested. Haiti's official languages are Creole and French, while the Colombian suspects speak Spanish.
Mr Charles said one of them had been given what the suspect believed was an arrest warrant for the president.
Most of the Colombian detainees have been identified as former soldiers, including a lieutenant-colonel.
Haitian police paraded them before the media.
Family members told Colombian media their loved ones had told them that they had been hired "to provide security" in Haiti.
After retiring from the army, many Colombian soldiers go on to work for security firms abroad, mainly in the United Arab Emirates, where they are valued for their training and experience in fighting armed groups.
Who hired the Colombians?
Haitian police announced on 11 July they had arrested a "key suspect" in the president's assassination.
Police chief Léon Charles alleged that Haitian national Christian Emmanuel Sanon had hired 26 of the 28-strong hit squad through a Miami-based company called CTU, run by Venezuelan national Tony Intriago.
Mr Charles said Mr Sanon was "the first person" that one of the Colombian suspects had called when police surrounded them.
He added that the 63-year-old doctor, who resides in Florida, had arrived in Haiti on a private jet in early June with "political motives".
Mr Charles said that police had found weapons, ammunition and a Drug Enforcement Administration cap in his possession.
He added that the suspects had called two other individuals while they tried to escape, but the police chief did not yet reveal their identities.
The police chief suggested that the Colombians might have been duped by Mr Sanon, who was planning to become Haiti's president.
"The initial mission that was given to these assailants was to protect the individual named Emmanuel Sanon, but afterwards the mission changed," he said without clarifying if all or any of the suspects had been briefed about the changes