Police say evidence found at the scene led to the arrest of Steven Carter, 34, of Upland.
Three men were found shot to death Monday morning at a house on the 1000 block of South Magnolia Avenue, near Mission Boulevard. When police arrived at the scene, they found one man dead on a driveway and two men dead inside a house located in the back of the property.
According to police, Carter and two other suspects intended to rob 31-year-old Brandon Perez, who lived in the back house, but the robbery didn't go as planned.
"It's a plausible scenario that there was some type of gunfire exchange," said Ontario Police Sgt. Dave McBride.
Perez was killed, along with the two other suspects, who were identified as 25-year-old Albert Lamar Thomas of Ontario and 27-year-old Aaron Rafael Phillip Andrews of Upland.
Neighbors said they heard dogs barking and what sounded like gunshots. Investigators found shotguns, rifles and marijuana inside the home.
Carter will be charged with three counts of murder.
Detectives believe that the incident was not a random act and say Perez was targeted, possibly because of drugs. The investigation is ongoing. Anyone with information was asked to call police at (909) 395-2764.