ELLSWORTH - The 24-year-old roofer accused of killing his coworker with a power saw at a River Falls-area job site pleaded not guilty this week to homicide and mayhem charges.

St. Louis, Mo., resident Miguel A. Navarro entered the pleas Sept. 5 after a preliminary hearing that moved the case into trial phase. Pierce County Circuit Court Judge Joe Boles set the case for a six-day jury trial beginning May 31, 2019.

The hearing brought grisly details from the alleged attack on Aug. 6 that left Israel Valles-Flores dead atop a roof at W10087 County Road FF, where a four-man crew was doing a roofing job.

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Pierce County Sheriff's Office investigator Collin Gilles described on the witness stand how, in interviews with authorities, crew member Marvin Fuentes Aguilar reported seeing Flores holding his neck "with blood coming out between his fingers" before watching Navarro cut at the man's body.

"(He) did a back-and-forth motion several times" with the saw, Gilles said, describing Aguilar's account.

Flores fell onto the garage portion of the roof, where Gilles said he was found with deep cuts to his neck, a cheek-to-cheek cut on his face, several cuts to both legs, along with cuts on his back and finger.

Aguilar and another roofer, Andres Vasquez, leapt from the roof, the investigator explained. Aguilar was "scared that Miguel was going to chase him," Gilles said.

Aguilar told Gilles that Navarro looked at him and said "he was going to (expletive) me or screw me," the investigator testified.

A bloody Milwaukee circular saw was found on the scene. Gilles said that included blood inside the exit port, where sawdust is normally found.

Gilles said Navarro was found with blood on his boots and pants. Defense attorney Jonathan Lundeen later asked Gilles if his client had blood on his hands; he didn't, Gilles replied.

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An affidavit attached to a search warrant filed in the case describes how bloody gloves were found "in plain sight" on the deck of the house.

A criminal complaint filed in the case describes how, in a recorded jail call, Navarro told someone the crew members had been teasing him about a one-night stand he'd had the previous night that left him upset - one of several reasons he allegedly mentioned for why "it" happened.

Gilles said neither Aguilar nor Vasquez admitted to teasing Navarro that day. Both men told investigators Navarro had previously said, "I'm a good person but you don't want to piss me off."

"When things are good, I'm good, but when things are bad, I'm bad," Gilles said, describing the witness accounts.

Lundeen later asked Gilles if the other roofers were aware that Navarro had gone to the homeowner's door and asked for help. Gilles said he hadn't known that.

Earlier in the hearing, Lundeen raised concerns that the Ramsey County Medical Office's autopsy report does not list the cause of death, which he argued could be from other factors, such as Flores' fall from the roof.

Boles concluded that the case can move forward since the low threshold that establishes grounds for probable cause was reached. That witnesses saw one man attacking another's neck with a power saw and "a reasonable person ought to know that that's going to cause death," the judge said.

A pretrial conference in the case was set for Oct. 25.