A multistate manhunt is underway for a Marine deserter accused of killing his mother’s boyfriend, authorities said Tuesday.

Michael Brown, 22, is wanted in the killing of Rodney Brown, 54, who died Saturday in Franklin County, Virginia, just south of Roanoke.

Michael Alexander Brown. Franklin County Sheriff's Office

Rodney Brown was found shot in his home Saturday, and the Franklin County Sheriff’s Office quickly found a suspect in Michael Brown, who deserted Marine Corps Base Camp Lejeune in North Carolina last month.

The sheriff's office announced Monday that it had obtained a warrant for Michael Brown's arrest for second-degree murder and felony use of a firearm. Michael Brown was last seen on surveillance footage from a store in the county Saturday, authorities said.

NBC affiliate WSLS in Roanoke reported that authorities are trying to establish a possible motive but that neighbors said they believe Michael Brown recently learned that Rodney Brown wasn’t his father, contrary to what he had believed for much of his life.

The Marine Corps told NBC News in a statement that the Naval Criminal Investigative Service is helping local authorities in the search.