EMBED >More News Videos Chopper 6 was over the scene of where a shooting victim was found on an off ramp of I-95 in New Castle, Delaware.

NEW CASTLE, Del. (WPVI) -- Delaware State Police are investigating a shooting on I-95 in New Castle that has left one person critically injured.Police responded to the report of an altercation between two men around 2:15 p.m. Monday on the Airport Road off-ramp.Arriving officers discovered one man had suffered a gunshot wound to the torso. He was transported to the hospital and remains in critical condition.A second man was taken into custody without incident.Desmond Chisholm had no idea what he walked into when he pulled over on the highway to help a 53-year-old man laying on the ground."First thing I thought was he had a heart attack or something so I pulled over," Chisholm said.Police say the 53-year-old man had just been shot in the upper torso, allegedly by the 28-year-old driver of a paratransit bus. They say the shooter began CPR and called 911."The guy who actually did the shooting approached me, and actually said 'I shot him in self-defense,'" said Chisholm.Delaware State Police Sergeant Richard Bratz said, "All indications point in the direction that this could be a road rage incident."Police say the shooting victim began following and flagging down the bus driver while traveling on Route 1 to Route 40."He noticed that the Dodge Durango went to the right side and appeared to be waving a cell phone at him as he was driving," Sgt. Bratz said.That allegedly continued onto I-95. The two men then pulled over, and the bus driver was allegedly attacked with pepper spray."After the pepper spray was discharged, the person driving the bus pulled out a handgun and fired it," said Sgt. Bratz.The paratransit bus could have been full of seniors who are part of the St. Francis Healthcare's Life Program. A fleet of buses, including the one involved in the incident, shuttle elderly participants from their homes to a Wilmington center daily. Luckily, no one but the driver was on board this time."This came as a shock to everyone. We want everyone to know no participants were on the van during the incident. Everyone is safe," said St. Francis Healthcare spokesperson Samantha Raftovich.St. Francis has a no firearms policy for employees. Part of the police investigation is determining if the shooter was legally carrying.Detectives are looking for more witnesses. No charges have been filed against the shooter who was taken into custody.-----