Tens of thousands of people in Omaha received a political mailing on Thursday. It comes from the Omaha Police Officer's Association and takes aim at two men running for office -- Frank Brown and Jim Vokal.

It questions whether they're serious about making neighborhoods safe.

Frank brown who's running for re-election to the city council isn't happy about it. "A half truth is still a lie. These are lies."

And neither is Jim Vokal who's running for mayor. "What this piece is all about the police union retaliating against me because O oppose spiking."

The Omaha Police Officers' Association mailing claims they blocked officers from monitoring high risk sex offenders in Omaha. "There's no reason why our Omaha patrol officers should not be able to conduct spot checks on high risk sex offenders that live in their districts," says Aaron Hanson with the Association.

To understand the controversy, we traced it back to the beginning -- and former Omaha Police officer Virgil Patlan.

In late 2005 -- while on-duty -- he would check on sex offenders to see if they were where they said they were.

He even sent one violator to prison for a year-and-a-half.

Eventually -- the police chief at the time, Thomas Warren told Officer Patlan to stop doing it -- saying that checking on sex offenders -- by state law -- was the job of the State Patrol and Douglas County Sheriff -- not Omaha Police.

After hearing that, Brown, Vokal and three other council members voted to keep it that way.

"The sheriff's office is doing it," says Frank Brown. "They wanted to latch on like an amoeba for what reason in order to do this."

"We have to do everything we can to monitor sex offenders," says Jim Vokal. "We are handcuffed and restricted by what state law is. And right now they give the authority to Douglas County."

The police union believes the law allows for it.

Reporter: "Your former boss, Chief Warren, said that officers should knock it off."

"Elected officials have to answer for their own actions," says Hanson.

The union points to one section of the state law that says: 'Local law enforcement agencies are requested, but not required, to periodically verify that the [sex offender] is still living at the listed address.'

The union believes that gives Omaha Police the go-ahead to do it.