A man charged with killing his sister's boyfriend was scheduled to enter a plea today in a case that has stumped detectives.

Jarrod Miller, 29, is suspected of pulling out a 380-caliber semi-automatic pistol without warning nine days ago at the couple's Alexander Valley home and shooting Timothy Neuer, 29, several times in front of his sister and another friend.

Miller showed up at the couple's home late on March 8, and Neuer asked him to leave the property, Sonoma County sheriff's officials said.

Investigatgors said Wednesday they have yet to uncover a clear motive.

"Everyone is at a complete loss," Lt. Dennis O'Leary said.

Neuer "was one of the people who was trying to help him," O'Leary said.

Miller, who grew up in Rio Nido, had returned to Sonoma County about four months ago after living in Las Vegas, family members said.

He stayed with his 24-year-old sister, Amanda "Mandy" Miller, and Neuer at the Alexander Valley Road home until the couple helped him find a place to live in Cloverdale, a family friend said.

Miller has refused to speak with detectives about the shooting, O'Leary said.

Miller's sister and another witness identified him as the shooter at the scene, sheriff's officials said. Windsor police officers pulled him over a short time later on Old Redwood Highway.

Miller was charged with first-degree murder, which could carry a 50-year-to-life sentence.

Read all of the PD's fire coverage here