Authorities say they have arrested a man they believe is connected to four killings that have shaken Northern Nevada and put residents on edge over the past two weeks.

Washoe County Sheriff Darin Balaam says Wilbur Ernesto Martinez Guzman, a Carson City resident who is either 19 or 20, was taken into custody Saturday afternoon on suspicion of burglary, possession of stolen property and immigration law violations. He’s being held in the Carson City Detention Center under 24-hour watch from medical and mental health personnel.

“At this stage in the investigation, we feel confident we have the evidence that will link him to all four homicides,” Balaam said at a Sunday afternoon press conference, adding that deputies don’t believe there are additional outstanding suspects.

The killings began in Gardnerville, the Douglas County community about 50 miles from Reno, when two women, Connie Koontz, 56, and Sophia Renken, 74, were killed inside their homes earlier this month only miles apart. The two victims were found Jan. 10 and Jan. 13 — within four days of each other.

Days later on Jan. 15, authorities began investigating two killings in Reno after Gerald David, 81, and Sharon David, 80, were found dead in their South Reno home. Gerald David was a former president of the Reno Rodeo, the Reno Gazette Journal reported.

Given the similarities between all four killings, the Federal Bureau of Investigation began aiding in the probe last week, the Associated Press reported. All of the killings relied on a firearm, appeared to target elderly victims and at least two involved property stolen from the homes.

Carson City Sheriff Kenny Furlong said law enforcement had received tips in the cases from Jan. 10 to Jan. 19 and deployed a multi-agency surveillance team on Friday to put Martinez Guzman under 24-hour surveillance.

They later learned from immigration officials that Martinez Guzman was likely in the country illegally and could be detained on those grounds. Furlong said activities that raised concern for public safety prompted immigration officials and Carson City deputies to take him into custody Saturday afternoon a few blocks south of the state capitol.

Officers also seized control of an apartment on Menlo Drive in Carson City, two vehicles, another family member and another apartment resident without incident, Furlong said.

Authorities say Martinez Guzman did not have interactions with Carson City deputies in the year he was apparently in the area. Officers declined to offer much about a motive, and did not elaborate why they zeroed in on Martinez Guzman except to say the investigative process and a tip led them to him.

Northern Nevada businesses selling guns and alarm systems told KOLO news that they saw an uptick in sales in the days following the killings.

“I want you to know we feel strongly we have the man responsible for this, and you can continue to go about your daily activities and live normal,” said Douglas County Sheriff Dan Coverley. “We worked hard to bring peace to you.”