RENO, Nevada -- Authorities investigating four recent killings in northern Nevada say murder charges are pending against a man suspected of being in the U.S. illegally.

Wilbur Martinez-Guzman, 19, was arrested Saturday in Carson City and is being held on possession of stolen property, burglary and immigration charges.

Authorities say they expect to file murder charges against him in the coming days in the shooting deaths of an elderly Reno couple and two women who lived near the town of Gardnerville.

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Washoe County Sheriff Darin Balaam told reporters Sunday he believed there were no other suspects, says CBS Reno affiliate KTVN-TV.

Wilbur Martinez-Guzman Carson City Sheriff's Office / KTVN-TV

"Investigators, patrol, forensic science, volunteers, dispatch, local, state and federal law enforcement agencies came together and worked tirelessly to get us to where we are in this investigation," Balaam said.

Carson City Sheriff Ken Furlong said at the news conference that federal immigration authorities told his office Martinez-Guzman had lived in Carson City for about a year and was in the country illegally.

Furlong said Monday he didn't know where Martinez-Guzman is originally from, and a message left with U.S. Immigration and Customs Enforcement wasn't immediately returned.

President Trump mentioned the killings Monday in a tweet calling for his long-promised border wall:

Four people in Nevada viciously robbed and killed by an illegal immigrant who should not have been in our Country. 26 people killed on the Border in a drug and gang related fight. Two large Caravans from Honduras broke into Mexico and are headed our way. We need a powerful Wall! — Donald J. Trump (@realDonaldTrump) January 21, 2019

Authorities say Connie Koontz, 56, was found dead Jan. 10 in her home in Gardnerville Ranchos, about 15 miles south of Carson City. Three days later, 74-year-old Sophia Renken was found dead in her home about a mile from where Koontz lived.

On Wednesday, the bodies of 81-year-old Gerald David, and his 80-year-old wife, Sharon, were found in their home on the southern edge of Reno, about 20 miles north of Carson City.

Furlong said the investigation is ongoing and it's too soon to comment on a possible motive. He said Martinez-Guzman didn't yet have an attorney who could comment on his behalf.