A motorist first spotted the dog weaving in and out of traffic on Marvin Road SE. The driver followed the dog to a nearby home, and when he looked in the window he saw what appeared to be a seriously injured man.
Deputies arrived moments later and found the 67-year-old victim bleeding from the neck.
"He'd suffered multiple stab wounds, and the stab wounds were caused by a screwdriver," said Greg Elwin with the Thurston County Sheriff's Office.
The victim was taken to the hospital for treatment, and deputies say his condition is "grave."
Jane Pennella is friends with the victim and was shocked to hear he had been attacked.
"I don't know what's happened. They just told me he was assaulted," she said. "I can't imagine who would doing anything like that to him."
Pennella said her friend uses a wheelchair and needs oxygen, but was ambulatory enough to drive.
It's unclear when the man was stabbed or what led up to the attack.
While investigating the Lacey incident, police received a 911 call about a fatal stabbing in Olympia. The caller said a woman had been stabbed in the neck, and he believed her son was responsible.
Using information they gathered at the Lacey crime scene, detectives came to the conclusion that the same man -- 30-year-old Tyler Lewis -- was responsible for both attacks.
The female victim may be the attacker's mother, and male victim is a former neighbor, police say.
Deputies arrested Lewis when he returned to the Olympia crime scene, according to Elwin. Detectives have interviewed Lewis, but haven't been able to come up with a motive for the crimes.
"He's been very calm an deliberate, kind of chillingly so, actually. That makes us wonder really deeply what caused this guy to go off and do these horrible things," Elwin said.