Park Police officers at Lafayette Square in Washington before a protest rally last year. (Astrid Riecken for The Washington Post)

The next acting chief of the U.S. Park Police is accused in a new complaint by the Fraternal Order of Police of arranging for criminal charges to be dismissed against defendants in San Francisco, including some reportedly drunken employees of the Presidio Trust who allegedly assaulted Park Police officers.

Gregory T. Monahan, 47, has been the assistant chief in charge of the San Francisco field office, but he is based at the Park Police’s Washington headquarters. He is set to become acting chief of the Park Police next week when Chief Robert MacLean takes over the Interior Department’s Office of Law Enforcement and Security, which oversees law enforcement, security and intelligence activities for seven federal agencies, including the Park Police. MacLean’s last day was Friday.

The complaint filed Friday by Michael E. Shalton Jr., the chairman of the Park Police chapter of the Fraternal Order of Police, alleges that on two occasions, people he identified as employees of the Presidio Trust in San Francisco were arrested and charged but that the head of the trust then contacted Monahan. Shalton said Monahan in turn contacted an assistant federal prosecutor in San Francisco, Denise Oki, who then dismissed all charges in both cases. Shalton provided emails to The Washington Post to back up his complaint, but some information was redacted.

The Presidio Trust is a federal agency that helps fund the Park Police in San Francisco through a partnership between the National Park Service and the Golden Gate National Parks Conservancy. Jean S. Fraser, the trust’s chief executive, who is accused by Shalton of asking Monahan to dismiss the charges against her employees, declined to comment Friday.

Monahan also declined to comment. Oki did not respond to emails seeking a response.

The deputy U.S. attorney in San Francisco, Joshua Eaton, issued a statement that confirmed that Oki did dismiss the charges “at the request of the agency that issued them.” Eaton said that “an agency request to dismiss a citation is not, in itself, improper” and that prosecutors had “no reason to believe that anyone in this office understood the requests referred to in the FOP’s letter were improper.” Eaton said that an independent review of the allegations would be conducted.

“We need a congressional investigation of the Park Police,” Shalton said in an interview. Shalton said he had written a ticket to a superior officer in the Washington area recently and that a captain “made sure the ticket was not turned in.” The Park Police have about 500 uniformed officers in Washington, New York and San Francisco.

Shalton filed his complaint to the Office of Special Counsel on a “Report Government Wrongdoing” form, and also sent a letter to Attorney General William P. Barr asking him to investigate “interference with the criminal justice system” by Park Police managers and the U.S. attorney’s office in Northern California. “FOP members go out and make arrests every day, risking their lives,” Shalton wrote to the attorney general, “and should not have to put up with a situation where a senior manager is able to have serious criminal and traffic matters dismissed by prosecutors just because he asks or does not like the optics of a situation.”

Shalton’s “optics” reference came from an email apparently sent from a Park Police official — whose name was redacted — to Oki in March 2018, after an episode at a bowling alley on the Presidio. Four Presidio Trust employees “were significantly intoxicated” and refused to leave the alley, Shalton wrote, and when Park Police officers arrived, two of the employees pushed or grabbed officers. Ten misdemeanor charges were filed against the four employees, including resisting arrest against three of them, according to Shalton.

The email to Oki, included with Shalton’s letter to Barr, states, “After consultation with Deputy Chief Gregory Monahan on today’s date, the U.S. Park Police is requesting that your office dismiss these tickets based on the timeliness of the issuance of the notice to appear in court and the optics connected to the personnel complaint.” Shalton said that the tickets were filed immediately, as required, and that at least one of the employees had filed a complaint against the officers in an attempt to get the charge quashed. Oki responded, “I will dismiss these citations per the agency’s request,” the emails show.

In a second incident, from March of last year, Park Police were called to check out an alarm at the Presidio golf course and encountered two employees who the officers believed were drunk. When the employees allegedly became belligerent and refused to provide identification, they were charged with failure to obey lawful orders.

Shalton submitted emails that show Oki again agreed to dismiss the charges and another email stating that “Monahan had called Denise to take care of tickets.” Shalton’s complaint says a mid-level commander objected to the case dismissals and was overruled by Monahan.

“The CEO of the Presidio Trust goes directly to Monahan any time her employees need help,” Shalton said. “That’s disgusting, and it needs to be addressed.”

The Park Police have also come under fire for their lack of transparency in the November 2017 slaying of unarmed motorist Bijan Ghaisar. Park Police officers Alejandro Amaya and Lucas Vinyard shot at Ghaisar as he sat behind the wheel of his Jeep Grand Cherokee, slowly driving away from them. MacLean declined to identify the officers or provide any information about the incident. A Fairfax County police officer recorded the incident on his in-car video camera, and Fairfax Police Chief Edwin C. Roessler Jr. released the tape in 2018, over federal objections, and later provided the officers’ names to the Ghaisar family as part of their lawsuit in the case. No decision has been made by the Justice Department or U.S. Attorney Jessie K. Liu of the District about whether to file charges in the case.

Justice Department officials declined to comment on Shalton’s complaint Friday.