A Yakima police detective with more than 18 years on the force was fired Tuesday for improperly sharing information with a potential witness in a double-murder case.

Detective Geoff Gronewald also was accused of failing to file timely reports in the case and for engaging in improper conduct, according to city officials. Yakima police Chief Dominic Rizzi described Gronewald’s actions as a breach of the public’s trust, but one he hopes does not tarnish the department’s reputation.

“We are worthy of (the public’s) trust because we are stepping forward and policing one of our own,” Rizzi said in a phone interview.

Gronewald was placed on paid administrative leave in February, when the investigation began. Rizzi said Gronewald was officially fired at the end of business Tuesday.

Rizzi’s decision to fire Gronewald follows a May 23 disciplinary hearing conducted by the Yakima Police Department. Rizzi said he delayed making a decision on Gronewald’s fate so that he could have adequate time to consider all the evidence.

Gronewald, who does not have a listed home phone number, could not be reached for comment.

Kristy Stell, one of Gronewald’s attorneys who represented him at the hearing, said she could not comment on the case until she consulted with him.

Tony Patlan, president of the Yakima Police Patrolman’s Association, disagreed with the decision, saying Gronewald was an exemplary officer with only one reprimand on his record. He said the union would be reviewing the matter with its attorney.

“As far as the union’s concerned, this is not over,” Patlan said.

According to an internal investigation report, Gronewald had a romantic relationship with Shannon Rosales, the former girlfriend of Michael Eby. Eby and Ryan Pederson were found shot to death Dec. 21, 2012, in a car near the Roza Recreation Area in the Yakima Canyon.

Four men were initially charged in the case, and two of them — Troy Whalen and Jose Pineda — pleaded guilty to reduced charges in return for testifying against the two remaining defendants, Heriberto Villa and Marco Gallegos. Gallegos is charged with two counts of aggravated first-degree murder and one count of first-degree unlawful possession of a firearm. Villa is facing charges of aggravated first-degree murder as well as first-degree rendering criminal assistance.

Whalen was initially charged with first-degree murder and first-degree rendering criminal assistance. In March, he pleaded guilty to first-degree manslaughter and first-degree rendering criminal assistance.

Pineda’s original charges were two counts of aggravated first-degree murder and a second-degree charge of unlawful possession of a firearm. He pleaded guilty to first-degree murder and first-degree rendering criminal assistance.

Whalen and Pineda are scheduled to be sentenced in August.

Police say Eby was killed at a house in Yakima, and that the defendants drove his body and Pederson into the canyon, where Pederson was shot to death.

Gronewald, who had used Eby as an informant, identified Eby’s body and participated in the interviews with the suspects, but he failed to file any formal reports in the case, according to the internal investigation report.

The report said Gronewald met Rosales during the murder investigation and started a romantic relationship with her. He was accused of revealing confidential information about the investigation to Rosales, including sending her text messages about what was being found during a search of the house in the case. During the search, Gronewald and Rosales exchanged 338 text messages.

Gronewald’s relationship with Rosales and the information he shared came to light on Feb. 14, when Rosales told prosecutors during a meeting with the victims’ families about information that was considered confidential. Supervising Deputy Prosecuting Attorney Troy Clements, who is handling the case, then informed the police department, which launched an investigation of Gronewald.

The investigative report released publicly blacked-out details about the confidential information.

The disclosures meant Rosales and her daughter could not be used as possible witnesses in the case because it would taint their testimony, the investigative report said.

Gronewald told investigators he had a brief relationship with Rosales, but had no recollection of telling her details about the case.

The incident was not the first time Gronewald got in trouble for an internal matter. The detective, who also earned the department’s Police Shield Award in 2013 for injuries he suffered when he tried to stop a fleeing suspect, received a verbal reprimand in October 2013 for improperly accessing reports by Yakima County sheriff’s deputies who responded to a domestic violence call at the home of a Yakima police official.

Gronewald and the police union have filed a federal lawsuit against the city, Rizzi, Public Records Officer Tammy Regimbal and a KIMA-TV reporter over the release of the investigative report prior to the May 23 disciplinary hearing. The suit, filed in April, sought to block the report’s release until Gronewald was given an opportunity to clear his name in a hearing.