Indianapolis ? Sniper attacks targeted two pickup trucks early Sunday on a busy highway near Seymour, killing one person and wounding a second, and police asked other motorists who had been through the area to check their vehicles for bullet holes.

Hours later, two more vehicles were struck by bullets on another four-lane highway about 100 miles away, but there was no immediate indication if the two cases were connected, police said.

One shot struck a southbound pickup on Interstate 65 shortly after midnight, killing one of its two passengers, police said. At about the same time, a bullet grazed the head of a passenger in another southbound pickup on the same highway.

Gov. Mitch Daniels ordered the Indiana National Guard to be placed on standby to help with the investigation if needed.

Police were left only with questions, unsure whether more than one sniper was involved, how many shots were fired or where the shooters could be headed.