Iberville Parish detectives said they don’t know why a 21-year-old Baton Rouge man shot himself in the head Wednesday morning while driving westbound on Interstate 10 over the Atchafalaya Basin, causing a two-hour backup near the Whiskey Bay exit.

“We’re just thankful he didn’t cause any other accident,” Maj. Ronnie Hebert, with the Iberville Parish Sheriff’s Office, said Wednesday afternoon.

“We did find a brand new box of bullets in the car. And he killed himself with a gun he purchased two days ago.”

Hebert identified the man as David Chimezie Chukwuebuka, a native of Nigeria who was living in Baton Rouge. Hebert said 911 dispatchers received a call around 10:15 a.m. saying a man was driving erratically down the elevated freeway while waving a gun.

After Chukwuebuka shot himself once in the head, Hebert said, his 2010 white Toyota Camry skid two miles along the freeway’s guard rail before stopping about 1½ miles east of the Whiskey Bay exit.

“We don’t know what the motive could be,” Hebert said.

Sheriff’s deputies had to close one lane of the interstate for about two hours Wednesday to clear the scene, causing at least 10 miles of congestion, according to the state Department of Transportation and Development.