SEYMOUR, Ind. (AP) – Sniper attacks targeted two pickup trucks early Sunday on a busy highway, 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.

“The Indiana State Police will treat these incidents as being connected until proven otherwise,” Sgt. Jerry Goodin said. “We’re literally scouring hundreds of miles of crime scene.”

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.

“We’re keeping an open mind,” Goodin said. “Wherever they’re from, we’re going to go after them.”

One pickup had a bullet hole near the top of the windshield on the passenger side. The second had a bullet hole in the middle of the windshield and a rear window was blown out.

About two hours later, bullets struck a tractor-trailer rig on Interstate 69 near Muncie, about 50 miles northeast of Indianapolis, state police said. Later, a parked, unattended SUV was struck at a service station in the same area. No one was injured. Police said both vehicles were struck multiple times but would not say where.

Police closed a 14-mile stretch of I-65 for eight hours after the Seymour shootings. The highway is part of the only direct route between Chicago and Florida and is heavily traveled at all hours, Goodin said.

Goodin asked motorists who had been through the Seymour area during the past week to check their vehicles for bullet holes.

Electronic highway signs around the state flashed a message to motorists: “Report suspicious overpass activities – call police.”

Police identified the man who was killed as Jerry L. Ross, 40, of New Albany.

The driver of the second pickup, Brandon Bonnesen of Anita, Iowa, said he and Robert John Otto Hartl, 25, of Audubon, Iowa, were driving to Florida for construction work when he heard a loud noise.

“I cussed a little bit and looked at my friend. He was all bent over and I said ‘You all right?” He said ‘I’m OK, keep going,”‘ Bonnesen said.

The bullet had grazed Hartl’s head near his left ear, Bonnesen said. He was treated at a local hospital and released.

In late 2003 and early 2004, a sniper in the Columbus, Ohio, area killed one person in a series of random highway shootings. Charles McCoy Jr., arrested in March 2004, was sentenced to 27 years in prison after pleading guilty.