On the night of Jan. 10, someone walked into a home tucked near the forests that blanket Nevada’s northwest border and fatally shot 56-year-old Connie Koontz, the authorities said. Three days later, again under the cover of darkness, someone walked into another Douglas County home about a mile up the road and shot and killed Sophia Renken, 74.
Then, three days after that, Washoe County sheriff’s deputies searched a home about 40 miles farther north on La Guardia Lane. There, they found 81-year-old Gerald David and his wife, Sharon David, 80, both with gunshot wounds; they, too, were dead.
For nine days, law enforcement officials from across the region banded together to both reassure and ready residents who had been shaken by what prosecutors would call “brutal murders.” Lock your doors and windows, the authorities said; turn on outdoor lights; keep your cellphones handy.
By Sunday — the 10th day of regionwide panic — they were able to deliver some calming news: A suspect was in custody; they believed the man, who they have varyingly identified as Wilbur or Wilber Martinez-Guzman, was responsible for all four homicides.
Mr. Martinez-Guzman, who is either 19 or 20 years old, had been arrested at a home on Saturday afternoon on felony burglary and immigration charges, Sheriff Ken Furlong of Carson City said, though prosecutors added that they intended to charge him with the murders. Law enforcement officials did not discuss the motive in the killings.
Immigration officials, Sheriff Furlong said, had notified law enforcement that Mr. Martinez-Guzman had been in the Carson City area for about a year, but “was likely in the United States illegally and was detainable.” Jail records show that he is under a hold from Immigration and Customs Enforcement, which Sheriff Furlong said prevented him from being released on bail. The agency did not immediately respond to a request for comment.
“Four people in Nevada viciously robbed and killed by an illegal immigrant who should not have been in our Country,” President Trump said in a tweet on Monday. “We need a powerful Wall!”
The disclosure that Mr. Martinez-Guzman may be in the United States illegally has thrust the case into a set of high-profile murders that President Trump has leveraged to bolster his arguments about immigration and the need for a wall along the country’s southwest border. The dispute over funding for such a wall remains at the center of a government shutdown.
The president has previously called attention to the murder of Mollie Tibbetts, a 20-year-old college student, who the police have said was killed by an undocumented immigrant from Mexico. (Her father has called on people to not exploit her death to promote a political agenda.) Mr. Trump also said it was “time to get tough on Border Security” after the authorities arrested a man in California in December who they said fatally shot a police officer and had entered the United States illegally.
In the meantime, friends and family of the four Nevada victims — some of whom flanked the police at the Sunday news conference — were left to grieve.
Eddie England, 70, who met Ms. Renken through the Carson Valley chapter of the Antique Automobile Club of America, said in an interview on Tuesday that four lives could have been saved if Mr. Martinez-Guzman had been expelled from the country.
He described Ms. Renken as an independent and tough woman who drove a 1930s Ford Model A. Still, she moved to Gardnerville in Douglas County a few years ago to be closer to people — a situation she felt would be safer, Mr. England said.
“And this,” he said, “is what happened to her.”
“It’s hard to take.”
Alan Squailia, a friend of Mr. David, described Gerald and his wife as “salt-of-the-earth people,” who were active community servants and animal lovers.
“If you needed a friend, and needed someone to help you, it was this couple,” Mr. Squailia, 75, said.
Looking at a photograph of Mr. Martinez-Guzman, Mr. Squailia said he could imagine that Mr. David would have invited the young man into his home if he had been looking for help.
“The whole city of Reno is devastated over this,” he said. “We still can’t wrap our minds around it.”