Mr Kirumira was a tough critic of Mr Kale Kayihura, the former police boss.
An outspoken and critical Ugandan policeman has been assassinated, a police spokesman said Sunday, in the latest in a series of murders of senior officers and politicians.
Mr Muhammad Kirumira and his female companion were attacked near his home in Bulenga, Wakiso District on Saturday.
"The Uganda Police Force is greatly concerned with the assassination of assistant superintendent of police Muhammad Kirumira at Bulenga last night," police spokesman Emillian Kayima said.
"He was with a lady whom we have been informed is not his wife but someone he knew, and she too succumbed to bullet wounds in the hospital where she was rushed for treatment."
Mr Kayima added that the assailants were reportedly travelling on a motorcycle, a tactic used in the killings of assistant inspector general of police Andrew Kaweesi in March as well as a senior public prosecutor in 2015, and others.
Mr Kirumira was a tough critic of Mr Kale Kayihura, the former police boss. He had said he was living in fear after being threatened with death.
He was suspended from his role as district commander in January after accusing his colleagues in a Facebook post of corruption and working with criminal gangs.
Shortly after he was arrested when heavily armed police forced their way into his house as he holed up resisting detention in an operation that took over five hours.
Mr Kirumira was awaiting trial on charges of criminal misconduct and abuse of authority at the time of his death.
A Police Disciplinary Court had in May recommended his demotion from Assistant Superintendent of Police to Assistant Inspector of Police.
Police Disciplinary Court chairman Denis Odongpiny found him guilty of abuse of authority contrary to section 44(1) and 24(a) of the Uganda Police code.
In his judgment, Mr Odongpiny noted that during Mr Kirumira's tenure as the Officer in Charge of Nansana Police Station, he and other police officers under his command went to the home of Kayizzi Kamada of Nansana West 2, Nakule Zone in Wakiso district, on April 19, 2014 and ordered his wife to vacate and relocate to another area, which was not under his mandate.
In March this year, President Yoweri Museveni fired the chief of police as well as the country's security minister in what was seen as a reaction to growing insecurity in the country.
In June this year ruling party lawmaker Ibrahim Abiriga was gunned down alongside his brother.
No one has been brought to book for any of the killings.
In June Museveni ordered that MPs should receive armoured escorts and snipers to protect them, a decision that divided lawmakers and raised concerns about the cost of such an operation.
Ugandan popstar turned politician Robert Kyagulanyi -- better known as Bobi Wine -- reacted to the news of Mr Kirumira's killing from the United States, where he is being treated after allegedly being tortured by Ugandan police after his arrest.
"Sadly, that is the country we are living in. No one is safe. Our country is bleeding. This is very painful," he wrote on Facebook.