Muskegon, MI – Muskegon County Sheriff’s K9 Rex passed away after being diagnosed with an aggressive form of blood cancer, the department announced on June 25.

His partner, Muskegon County Deputy Jamie Ottinger, noticed a rapidly-growing lump on K9 Rex’s back and hip, which doubled in size overnight and caused him to limp, the department said in a June 20 Facebook post.

K9 Rex underwent emergency exploratory surgery on June 13, and was subsequently diagnosed with subcutaneous hemangiosarcoma, the agency explained.

Following the procedure, K9 Rex was taken to Grand Rapids for further cancer treatment.

In the wake of K9 Rex’s diagnosis, Deputy Ottinger organized an open house so K9 Rex’s fellow officers and friends could gather to be with him and thank him one last time, the Shoreline Media Group reported.

Instead, the June 28 gathering became a well-attended memorial service.

K9 Rex, a “high energy” German Shepard who was born in the Netherlands, was “hand-picked” by the department in 2012, the sheriff’s office said.

After he completed his pre-service training with the Southfield Police Department, K9 Rex joined Deputy Ottinger for a five-week training program at the Oakland Community College.

The partners were inseparable during the six years of service that followed.

“He worked with me and then he came home with me,” Deputy Ottinger told the Shoreline Media Group. “He worked hard for me.”

K9 Rex was trained as a tracker, narcotics detector, and protector. He also made regular appearances at community events and schools, and assisted nearby law enforcement agencies as needed.

“K9 Rex has touched many lives while serving Muskegon County,” the sheriff’s office said.

Our thoughts and prayers are with the Muskegon County Sheriff’s Office and Deputy Jamie Ottinger in the loss of K9 Rex.