One man is dead after the 18-wheeler he was driving rolled over this morning on I-95 near mile marker 241, just south of the Medway exit.Police say 50-year old Donald Pepin of Mattawamkeag was killed when the chip truck he was driving rolled over and hit a guardrail just after 11:00 a.m.State Police say witnesses reported seeing Pepin pass two-vehicles before he returned to the travel lane and lost control of the truck. Authorities are not sure what caused the accident. “At this point we don’t believe the sun was a factor,” says Sgt. David Millett of the Maine State Police. “Obviously it’s still under investigation. We’re going to reconstruct the crash and just continue to investigate it and interview anybody that may have seen something.”Police are asking anyone who may have witnessed the crash to call them at 866-2122.