When he encountered Victor Duffy Jr. outside Duffy’s home in June, Tukwila police Officer Joshua Vivet said he quickly sensed the 25-year-old man was suffering from acute mental illness.

Duffy Jr. was holding a golf club and was ranting about how his sister, his mother and his mother’s common-law husband were strangers who didn’t belong in his home.

Vivet, testifying this week in the King County inquest into Duffy Jr.’s death, described the scene in the home as “chaotic,” with the family members yelling at each other. Vivet wanted to speak with Duffy Jr. in a calmer environment to determine what sort of help he needed.

But within minutes, after officers determined that he needed to be involuntarily committed to a mental-health facility, Duffy Jr. was swinging at police and refusing to comply with their attempts to pat him down for weapons. Vivet said Duffy Jr. seemed to possess “superhuman strength;” he shoved two officers away and appeared unaffected after being shot with Taser barbs and doused with pepper spray.

“Duffy’s whole mood seemed to change when I touched him [to pat him down],” Vivet said.

Duffy Jr. ran out of the house in the 5600 block of South 150th Place, leapt from the porch and hurt his leg. He continued to fight police until they managed to handcuff him and strap him on a gurney, Vivet said.

Later that day, Duffy Jr. was pronounced dead. The King County Medical Examiner’s Office has ruled his death was caused by “sudden death associated with the manifestations of excited delirium and following physical restraint.” The manner of death has not been determined.

The inquest, ordered by county Executive Dow Constantine, is a fact-finding hearing conducted before a district-court jury to determine the causes and circumstances of Duffy Jr’s death. At the conclusion, jurors will be asked to answer questions to determine the significant factual issues in the case, and it is not their purpose to decide whether any person or agency is civilly or criminally liable.

Lawyers representing Duffy Jr.’s family, the King County Prosecutor’s Office and the city of Tukwila and the Tukwila Police Department are participating in the inquest.

Duffy Jr.’s family has filed a lawsuit seeking at least $15 million in damages from the city.

Earlier this week, Duffy Jr.’s sister, Patrice Brown, and her mother, Deann Mills, testified that they told police and 911 dispatchers that Duffy Jr. was mentally ill and off his medications. Mills said she also asked officers not to use a Taser on her son, which she claims they did even after he injured his leg.

Medics were called, and Duffy Jr. was put inside an emergency-medical vehicle for about 40 minutes; during that time, his relatives weren’t allowed to see or speak to him, the suit says.

One officer told Mills her son was “sleeping” — but according to the lawsuit, Duffy Jr. was already dead, which officers concealed from the family.

According to a news release issued by Tukwila police shortly after the incident, Duffy Jr. began to experience “breathing difficulties” while he was in an ambulance and died later at Harborview Medical Center in Seattle.

Jennifer Sullivan: 206-464-8294 or jensullivan@seattletimes.com. On Twitter @SeattleSullivan

Information from Seattle Times archives is included in this report.