Rony Yahir Alvarenga-Rivera of Valley Stream charged in fatal stabbings of neighbor, Wendy's co-worker

A Valley Stream man allegedly confessed to stabbing a neighbor and a co-worker in separate incidents that left two women dead, according to Nassau County police and a prosecutor.

Police charged Rony Yahir Alvarenga-Rivera, 22, with first-degree murder and two counts of second-degree murder after he allegedly killed a woman at a home they shared in Valley Stream and then a co-worker at Wendy's in Island Park, according to police.

The stabbings occurred about 3½ hours apart late Thursday night into early Friday, police said.

Alvarenga-Rivera pleaded not guilty and was held without bail at his arraignment in First District Court in Hempstead on Saturday morning.

Nassau Det. Lt. George D'Arienzo said both victims were killed by "multiple stab wounds to the neck and torso," adding that the suspect appeared to be fueled by "anger."

D'Arienzo was joined by Police Commissioner Patrick Ryder, Nassau County Executive Bruce Blakeman and other police officials at a news conference at police headquarters on Saturday afternoon to discuss the arrest.

Police have not identified the victims pending family notification.

At the arraignment, the prosecutor said the suspect contacted police to turn himself in after the killings and gave a "full confession." Alvarenga-Rivera allegedly stabbed his upstairs neighbor, a 32-year-old, upward of 50 times "without warning," and then left her "in a pool of her own blood," the prosecutor said.

Alvarenga-Rivera later went to the Wendy's on Austin Boulevard and allegedly stabbed and killed his 42-year-old co-worker when she went to take out the garbage, the prosecutor said.

Police observed blood on Alvarenga-Rivera's clothes and cuts on his hands when he turned himself in, the prosecutor said.

Alvarenga-Rivera was represented by a court-appointed attorney who declined to comment after the arraignment.

Police account

D'Arienzo provided a timeline of events, starting when police were first notified of a person with a knife at 12:30 a.m. Friday at Wendy's. Responding officers found the victim "laying on the ground with blood," D'Arienzo said.

He said the victim has two children in the United States who are ages 8 and 1½.

During the investigation, D'Arienzo said police were notified of someone seeking police assistance at 169 Atlantic Ave. — the location of a 7-Eleven — in Lynbrook.

Lynbrook Police Chief Brian Paladino told Newsday on Friday that Alvarenga-Rivera had asked a counter clerk at the 7-Eleven to call police. Lynbrook police then responded and notified Nassau police.

Alvarenga-Rivera then admitted to officers that he had killed a woman, D'Arienzo said.

"He asked to see the police," D'Arienzo said. "When police arrived he said he had killed somebody that night."

Police discovered the second victim at 90 W. Mineola Ave. in Valley Stream, where the woman had been killed around 9 p.m. Thursday, according to police.

Alvarenga-Rivera and the female victim lived in the same house, renting separate bedrooms in a home with shared spaces, D'Arienzo said.

He said he was "not aware" of a "specific domestic relationship between those two."

Police did not provide additional information on the motive or whether the two victims knew each other.

'Very shocking'

At Wendy's in Island Park on Saturday, the fast-food restaurant was open as normal.

Elizabeth Infante, 20, a cashier, described the events as "very shocking."

She said she was working on the night of the killing in the drive-through and discovered her co-worker's body near the dumpster. She went inside to tell her manager, at which point police arrived, she said.

She said the victim worked in the kitchen and "got along with everybody."

"She was very nice. Very sweet. She would always make everybody laugh," she said.

Rivera had no prior arrests and no known interactions with police, D'Arienzo said.

At the news conference, Blakeman, a Republican running for governor against Democrat Kathy Hochul, used the killings to defend the county's partnership with U.S. Immigration and Customs Enforcement through its 287(g) program.

He said the suspect was a native of El Salvador who came to the United States as an "unaccompanied minor" in 2016 when he was 12 years old.

The 287(g) program allows police detectives to work with federal authorities as they seek immigrants without legal status to arrest and deport.

"We are deeply saddened by this tragic incident and our hearts are with the victim’s family and loved ones," Wendy's representatives wrote in a statement on behalf of the franchisee. "The safety and well-being of our employees remains a top priority, and our focus right now is on supporting our team during this difficult time."