McCartney, 34, of Yelm was shot while responding to a burglary call in the Fredrickson area.
It was not immediately known who shot one of the suspects, or whether the deputy managed to return fire.
McCartney was married and had three young sons, according to KOMO-TV.
"He chased after him and there were shots fired", sheriff's spokesman Ed Troyer said in an interview.
When other law enforcement officers arrived, they found one of the suspected burglars dead of a gunshot wound. "We are with his family now, and we ask that you please keep his family, friends and our department in your thoughts and prayers". Police believe that handgun was used to shoot McCartney.
Police say the suspect is described as a tall, thin, mixed race or white male, with a large pointy nose, curly dark hair in a ponytail, and pock marks on the right side of his face.
After the deputy was taken to the hospital, Pierce County Sheriff Paul Pastour called the shooting a loss to the entire community.
Bethel School District canceled all classes for Monday out of "an abundance of caution", it reported on its Facebook page.
Officials say numerous streets are being closed in the area as law enforcement conducts a search for the gunman.
A memorial fund was set up to benefit his wife and children.