SWAMPSCOTT – Humphrey Street was reopened just after 1 p.m. Tuesday. It was closed from the Gibbs gas station to Cedar Hill Terrace for several hours as police investigated an accident involving an MBTA police cruiser.The accident occurred near the intersection of Humphrey Street and Puritan Road and sent an MBTA police officer to the hospital.MBTA Spokesman Joe Pesaturo said the injured officer is 34 years old and has been with the Transit Police for eight years.Matt Kimball, 18, was driving alongside the MBTA cruiser when the accident occurred.”He was driving in the middle of the fork (in the road),” Kimball said. “He was leaning forward and slumped over the wheel ? He was making weird body movements. He hit the accelerator and smashed into the traffic light.”Kimball, who was on his way to work at Swampscott Parks & Recreation, said it looked like a demolition derby.”He crashed into signs and cars in the parking lot,” he said. “His head had smashed into the windshield. He was drooling and his tongue was hanging out. I could tell he was having a seizure.”Kimball and several bystanders rushed to the driver’s aid but they had trouble getting him out of the vehicle.”He freaked out,” Kimball said. “He was screaming for help but went crazy when anyone tried to get near him.”James Dawson, who owns Small Wheels and Humphrey Motors, said the driver of the MBTA police cruiser was disorientated and combative when bystanders tried to assist him from the vehicle.”It took four or five guys to hold him down until the ambulance got here,” Dawson said.In addition to hitting the traffic signal, the officer also hit at least two signs and several parked vehicles including a white van that had been dropped off at Humphrey Motors for repairs.Salem resident Amy O’Keefe was exiting Humphrey Motors when the accident occurred.”I saw him coming way over near the sidewalk,” she said. “If I had been any closer to the street he would have hit me head on. The crash was so loud. It’s a miracle no one got killed.”MBTA Lt. Commander Robert Lenehan would not release the identity of the driver because his family had not been notified.”He was on routine patrol,” Lenehan said. “He was checking bus stops.”Pesaturo said the accident remains under investigation.