SEYMOUR, Ind. -- Indiana law enforcement agencies and the FBI are embarking on a full-scale effort to find the person or persons who were involved in a series of sniper shootings on two interstates early Sunday morning that left one man dead and another man injured.

Indiana State Police, the Indiana National Guard, the Department of Homeland Security and local law enforcement agencies are involved or on notice for possible involvement in the investigation.

Ballistics evidence gathered from the scenes of the shootings on Interstate 65 in Jackson County and on Interstate 69 in Delaware County will be compared to determine what type of weapon was involved.

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Video: Investigators Ramp Up Search For Interstate Sniper

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Police talked with officials from Arizona and Ohio, two states that have dealt with sniper shootings in the recent past.

"We're trying to get information from them that could possibly help us in our investigation here in Indiana," said Indiana State Police Sgt. Jerry Goodin.

Police are also asking for help from the public. Road signs have been installed on highways asking people to watch for unusual activity on overpasses. Patrols have also been beefed up on interstates throughout the state.

"We have tapped every available trooper in the state of Indiana ... and they're going to be out there working over the next several days to let people know that it's going to be safe to drive up and down the roadway," Goodin said.

Jerry Ross, 40, of New Albany was killed in the first shooting at mile marker 52 on Interstate 65, near Seymour when the pickup truck he was riding in was fired upon. That shooting happened shortly after midnight. Two other people in that truck were not hurt.

Moments later, another pickup truck was shot at. The driver of that truck stopped at a Shell station nearby and called 911. A bullet grazed Robert Hartl, 25, of Audubon, Iowa, near his ear. Hartl was not seriously injured.

About two hours later, more shootings were reported on Interstate 69 at mile marker 42 in Delaware County. A tractor-trailer and abandoned vehicle were fired upon. No one was hurt in those shootings.

Investigators stopped short of a definitive statement that the shootings, about 100 miles apart, are related, but are operating on the assumption that they are.

Investigators Gather Details Of Shootings

Police are not releasing much information about the ongoing investigation, but the focus has centered on interstate overpasses.

Investigators walked on overpasses both Sunday and Monday, hoping to retrace steps that the sniper or snipers might have walked.

Police said the shots could have been fired from overpasses, or could have been fired from the woods adjacent to the interstate.

Police asked businesses along I-65 and I-69 to save any surveillance tapes they might have from over the weekend. Investigators hope additional clues might be found on those tapes.

Investigators also asked motorists who have traveled I-65 and I-69 within the past week to inspect their vehicles for bullet holes. Officials advised that sounds that motorists might have thought were rocks could have been bullets.

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.

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 resources 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.

Stay with 6News and TheIndyChannel.com for coverage of this developing story.