The incident began at about 11 p.m. in the 25700 block of 164th Street East when the two occupants of the home heard someone trying to break in and called 911, said Detective Sgt. Brian Lund of the Pierce County Sheriff's Office.
Lund said the 21-year-old suspect had crashed a car through a locked gate, hit some parked cars, then got out and broke through the door of the home.
The 67-year-old homeowner, who has a heart condition, grabbed a gun and went to investigate after calling 911. The intruder confronted the homeowner and began punching him around, said Pierce County sheriff's spokesman Ed Troyer.
At that point, the homeowner opened fire, striking and killing the intruder inside the home.
The homeowner sustained minor injuries in the struggle and was taken to a local hospital. He will not be arrested, Troyer said, adding that he does not expect that the prosecutor will file charges against him.
The home's occupants said they did not know the intruder, who "reeked" of marijuana, Troyer said. He said toxicology tests will show if the suspect had other drugs in his system.
Deputies also interviewed neighbors, who said they heard the suspect's car revving its engine before crashing through the gate.