Lesotho's Prime Minister Thomas Thabane, 80, is to be charged with the murder of his estranged wife Lipolelo Thabane, police have said.
Mr Thabane announced he would be stepping down in July because of old age, without commenting about the case.
His current wife Maesaiah Thabane has already been charged with the murder.
He would be the first African leader to be charged with a domestic murder while in office, in a case that has shocked the tiny mountain kingdom.
Lipolelo, 58, was shot dead two days before Mr Thabane became prime minister in 2017.
At the time, he described her killing as "senseless" but police now accuse him of being involved in her killing.
"The prime minister is going to be charged with the murder," Deputy Commissioner of Police Paseka Mokete was quoted by Reuters news agency as saying.
"The police are preparing directives and he will probably be charged tomorrow [Friday]," he added.
What does the prime minister say?
Mr Thabane said on state radio that he had served the nation "diligently" and he would retire at the end of July, Reuters reports.
"I've worked for a peaceful and stable Lesotho. Today... at my age, I have lost most of my energy," he was quoted as saying.
The ruling All Basotho Convention had given him a deadline of Thursday to resign.
Constitutional crisis looms
Lesotho's prime minister is not going down without a fight - his party, the All Basotho Convention (ABC) and its leadership, were expecting him to accept an ultimatum to step down ahead of the opening of parliament on Friday but he has refused.
But it now looks highly unlikely that he will be appearing at parliament on Friday as planned.
It's a desperate time for Mr Thabane, who has lost favour with his allies in this coalition government.
He is now seen as a sinking ship and they do not want to go down with him.
The prime minister is running out of time and room to manoeuvre - the country's police want him charged and hauled before a court, all by the end of this week.
His arrest will not only be a great humiliation to the prime minister but could also plunge the country in a constitutional crisis - it's not every day that a sitting leader is charged with a crime.
How did the murder take place?
Lipolelo was gunned down at close range on the side of a dirt road while returning to her home in a small village on the outskirts of the capital, Maseru.
She was involved in bitter divorce proceedings with Mr Thabane when she was killed.
At the time, the prime minister was living with Maesaiah, 42, as if she were his wife.
But Lipolelo had already won a separate legal battle to be recognised as first lady, as opposed to Maesaiah.
Maesaiah accompanied Mr Thabane to his inauguration, following his estranged wife's death.
Two months later she and Mr Thabane got married in a Catholic ceremony held at a packed stadium in Maseru.
Maesaiah was charged with her rival's murder on 5 February, and is out on bail of about $67 (£52).
She has also been charged with the attempted murder of a family friend Thato Sibolla, who was with Lipolelo at the time of the shooting and is expected to be a key witness in the murder case.
Maesaiah has not yet been asked to enter a plea.