A Texas man accused of killing two people while randomly firing his gun along an Oklahoma interstate was charged Monday with first-degree murder.

Jeremy Doss Hardy, 36, of Pasadena, Texas, is accused in the deaths of Jeffrey Kent Powell of Arapaho and Billie Jean West of Lone Wolf. Both were traveling on Interstate 40, west of Oklahoma City, when they were shot last week.

Hardy was arrested about an hour after reports came in of a man in a pickup truck firing a gun along Interstate 40. He was initially jailed for driving under the influence. But prosecutors added two first-degree murder charges Monday during a hearing in Custer County court, according to The Oklahoman newspaper and KOCO-TV in Oklahoma City.

Both the Oklahoma State Bureau of Investigation and the sheriff of Custer County, where Hardy was arrested, said the case is being investigated as possible road rage. The agencies said they had no indication the shooter knew the victims.

In an interview with The Oklahoman, Hardy's father, Robert Hardy, said the reports seemed out of character for his son. He questioned whether authorities may have stopped his son by mistake.

"It's definitely not the way he was taught or the way he's always been," Robert Hardy told the newspaper on Thursday, before charges were filed. "Weren't there a lot of black four-door pickups on the road? . That's a pretty common vehicle for this part of the country. I'm praying that that's not something he's capable of doing."