SEYMOUR, Ind. -- One man was killed and another was injured in sniper shootings early Sunday morning along Interstate 65 in Seymour, two hours before more shootings in Delaware County along Interstate 69.

Police said they haven't established a clear connection between the shootings, but are treating the shootings as though they are connected.

Jerry Ross, 40, of New Albany was killed in the first shooting, which happened just after midnight at mile marker 52 southbound. Two other people in the pickup truck Ross was in were not injured.

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1 Killed, 1 Injured In Interstate Sniper Shootings

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Moments later, another pickup truck was shot at. The driver of that truck stopped at a Shell gas station nearby. A bullet grazed Robert Hartl, 25, of Audubon, Iowa, near his ear. Hartl, a passenger in the truck, was taken to a hospital, where he was treated and released.

Brandon Bonnesen, who was driving the second truck, said he tried to remain calm in spite of what had just happened.

"I cussed a little bit and I looked at my friend and said, 'Are you all right?' because he was bent over, and he said, 'Oh no, I'm fine. Just go,'" Bonnesen said.

Police aren't sure how many people are involved or if the shots were fired from an overpass or another vehicle.

"Right now, we don't know. We don't know if we have one or if we have two or three (shooters). We're just trying to piece everything together and trying to find out," said Indiana State Police Sgt. Jerry Goodin.

Police don't know what type of gun was used and haven't found any shell casings. They hope witnesses will come forward and asked drivers who went through the area early Sunday morning to check their vehicles for bullet holes, and to contact them if they find any.

I-65 was closed for eight hours as investigators tried to determine who had fired the shots and from where they were fired.

"We're deeply concerned about it, and that's why we're calling out everybody that we have," Goodin said. "We're going try to get this person apprehended, or people apprehended, as quickly as possible. We're not going to stop on it until we get that done."

Two Hours Later: More Interstate Shootings

About two hours later, two more sniper shootings were reported just northeast of Muncie on Interstate 69.

The shootings happened at about 2:30 a.m. at mile marker 42. The state police post in Redkey responded to the shootings, unaware of what had transpired two hours earlier in Seymour.

In the Delaware County shootings, a tractor-trailer and abandoned vehicle were hit. No one was injured.

Police are not sure from where the shots were fired, but are working to make a determination.

Investigators asked anyone with information about the shootings to call the State Police Tipline at 1-800-622-4962. That number connects to the state police Task Force Hotline. Anyone who lives outside of Indiana should call 317-232-8250 with tips.

Governor Offers National Guard, Homeland Security Support

Gov. Mitch Daniels has pledged the support of the Indiana National Guard and the state Department of Homeland Security in assisting the state police in the investigation of Sunday's shootings.

"We will not treat this just as a criminal act. We'll use any and all resourced to find the person or persons responsible, and, in the meantime, we'll make sure people can go about their business safely and confidently," Daniels said in a statement released Sunday.

Indiana State Police briefed Daniels about developments in their investigation throughout the day.

6News' Tanya Spencer and Dan Spehler contributed to this report.