According to police, Bruce Danforth, 45, was driving a Mercury Sable north on Route 16 when his vehicle crossed over a double-yellow line into oncoming traffic. The Sable collided head-on into a Ford Taurus that was carrying the on-duty agents, police said. Police are still looking into what may have contributed or caused the accident.
Danforth died at the scene, police said, and his girlfriend, 35 and friend, 21, were hospitalized.
All four of the Secret Service officers were transferred to Frisbie Memorial Hospital for treatment, Wakefield Police Chief Kenneth Fifield said in a statement. Their names have not been released.
"At this time, our personnel have sustained what is described as serious, but non-life-threatening injuries," Secret Service officials said in a statement today. "Please join us as we keep all the victims of this accident and their families in our thoughts and prayers."
Police said the agents were on protective duty Tuesday night at an event for Democratic presidential candidate Hillary Clinton in Berlin, north of where the crash happened at about 7 p.m.
"I was saddened and concerned to hear about the serious accident that occurred last night in New Hampshire in which four Secret Service agents were injured and a passenger in a second car killed," Clinton said in a statement to ABC News today. "My husband and I send our prayers and condolences to all the victims and their families. We are grateful everyday for the service, dedication, and professionalism of the U.S. Secret Service."
Danforth did not possess an valid driver's license at the time of the crash, was on probation, and had an "extensive criminal history," New Hampshire police said in a press conference Wednesday. Police do not yet know why Danforth's license was invalid.
A joint investigation with the Wakefield Police Department and New Hampshire State Police is ongoing.