It was trumpeted as the biggest bounty in California's living memory but the $1m reward for the capture of Christopher Dorner, a disgruntled former Los Angeles police officer, has now triggered a row over the refusal of some donors to pay up.

The city of Riverside has rescinded its $100,000 contribution, and others are expected to follow, on the grounds that the circumstances of the siege, and the self-inflicted gunshot wound that killed Dorner last month, did not warrant a reward.

"Because the conditions were not met, there will not be a payment of a reward by the city," Riverside spokeswoman Cindie Perry said on Tuesday.

Critics accused Riverside of welching on a promise and undermining future bounties.

Dorner's 10-day vendetta against law enforcers and their families claimed four lives and triggered a huge manhunt before ending in a gun battle and conflagration at a mountain cabin near Big Bear, east of Los Angeles.

Authorities, police unions, civic organisations and private donors pledged more than $1m for information leading to his arrest and conviction.

Much of the climax to the hunt for Christopher Dorner unfolded live on television. Photograph: Uncredited/AP

Three people have claimed the money: a husband and wife Dorner tied up before stealing their vehicle, and a man whose pickup truck Dorner hijacked a short time later in an attempt to evade the dragnet around Big Bear.

All three alerted authorities but the Riverside mayor Rusty Bailey said the fugitive was not arrested or convicted. "Thank you for making the phone calls, for your part in bringing Chris Dorner to an end. Unfortunately, it wasn't through the justice system, and that's what our precedence has created, and our process and resolution provided for."

An unstated, additional reason, according to the Los Angeles Times, is a moral qualm that the trio alerted police because they were victims, and that they should not profit from their brief, non-violent encounters with the killer.

"I've spoken with some groups – including a few that are substantial – that have already decided to withdraw their pledges," said Ron Cottingham, president of the Peace Officers Research Association of California, which has put its own pledge on hold pending a final decision. "They said the reward doesn't fit their criteria."

Critics have responded with concern and scorn. Kirk Albanese, the deputy chief of the Los Angeles police department, said it would be "disingenuous" to withhold payment because Dorner died before being put on trial, and that it could undermine future bounties.

Dorner, 33, a former navy reservist, held a grudge because the LAPD sacked him in 2008 saying he had falsely accused a colleague of kicking a homeless man. Before his rampage he posted a lengthy online "manifesto" that accused the department of racism and deceit.

His revenge allegedly began on 3 February with the murder of Monica Quan, 28, the daughter of a retired police captain, and her fiance, Keith Lawrence, 27. They were shot dead in their car.

Four days later a police officer Michael Crain, 34, was killed in Riverside and two others were wounded. On February 12 Dorner killed a San Bernardino detective, Jeremiah MacKay, and wounded a colleague as he was cornered on the snowy slopes of Angelus Oaks near Big Bear.