A Seattle police officer is under criminal investigation after patrol-car video raised questions over his use of force on a handcuffed woman, the department announced.

In a written statement released Thursday evening, Police Chief Kathleen O’Toole said the officer has been relieved of duty and, in keeping with department policy, placed on paid leave while the case is investigated.

The carefully worded statement did not describe details of the incident, but sources familiar with the matter, speaking on condition of anonymity, said the officer punched the handcuffed woman after she kicked him.

The officer, who works in the South Precinct, was not identified in the statement, but sources identified him as Adley E. Shepherd, 38, who joined the department in 2005.

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The incident occurred Sunday, after the officer arrested the woman in a domestic-violence incident, O’Toole said in the statement.

“During the course of the incident, both the officer and the female were injured,” O’Toole said.

Because of the injuries, the department activated its Force Investigation Team (FIT), the statement said.

Representatives of the department’s Office of Professional Accountability (OPA), which handles internal investigations, also responded to investigate, according to O’Toole.

“OPA and FIT investigators reviewed digital in-car video and, based on that review, determined that additional investigation is warranted,” the statement said.

The department is conducting a criminal investigation, said Sgt. Sean Whitcomb, a department spokesman. Sources said the woman kicked Shepherd as he was putting her in his patrol car.

The officer then punched her in the face, according to the sources.

O’Toole revealed she has asked the State Patrol to assist in the investigation and briefed U.S. Attorney Jenny Durkan and the FBI.

The case is being investigated as a potential felony because of the nature of the injury to the woman, according to one source.

It was not immediately clear how the incident came to the attention of department officials.

Ron Smith, president of the Seattle Police Officers’ Guild, which represents sergeants and officers, said he was told the arrested woman did not want to get into the patrol car. He said it was his understanding that Shepherd was “kicked in the head trying to put her in the patrol car.”

Smith said he was told Shepherd then punched the woman in the face.

Shepherd was treated at Harborview Medical Center, Smith said.

As is normal protocol when an officer is placed on paid leave, Shepherd’s gun and badge were taken from him, Smith said.

Smith said he wants to review the patrol-car video because he has heard different versions of what occurred.

Under standard policy, the OPA won’t do its own inquiry until the criminal case is completed.

O’Toole inherited the case Monday, the day she was sworn into the job.

The department is under a federal consent decree, requiring it to adopt reforms to curtail excessive force and biased policing.

The FIT team was created as part of the reforms, which include strengthened efforts to investigate and track use of force.

Smith said he believes the incident was handled properly under the parameters of the “FIT model” established under the consent decree.

The city entered into the consent decree in July 2012, after the Department of Justice found a pattern or practice of excessive force in the department.

Shepherd was involved in a high-profile incident in 2009 that led to a 10-day suspension. He and a Seattle police sergeant were disciplined after they released a domestic-violence suspect who then returned home and killed his roommate.

Shepherd and Sgt. Roger Rusness were disciplined for the decision to release Valente Alvarez-Guerrero instead of booking him into the King County Jail after he was arrested in an assault on his roommate, according to internal-investigation documents.

Material from Times staff reporter Jennifer Sullivan, news researcher Miyoko Wolf and Times archives was used in this report.

Steve Miletich: 206-464-3302 or smiletich@seattletimes.com On Twitter @stevemiletich