Vlassopolous, 39, told The Associated Press that he was headed to his job at Engine Co. 18 near Capitol Hill in the District when he spotted a fire in the distance. It was shortly before 5 a.m.
He said he pulled over and walked to a highway bridge over Seneca Creek and saw the tanker in the water.
He grabbed a light from his vehicle and made his way down the bank. He saw the two men on the cab trying to help Kinder, who was in the frigid water.
Vlassopolous said he took off his coat and shoes, jumped into the water and reached Kinder, whom he helped lift up to the two men.
According to a Maryland State Police report, Kinder was southbound on I-270 when he lost control for some unknown reason and hit the guard rail and jersey barrier before the rig went down the bank and into the creek.
The tanker, which landed on its side in the water, was empty, but the fuel that powered it was burning.
Adna Fulton, owner of AC&T, said Kinder, who drove for the company for 10 years, was en route to Fairfax, Va., for a load of gasoline.
"I'd like to personally thank him (Vlassopolous)," Fulton said. "We're all very grateful. He (Kinder) came very close to losing his life. He told me some guy in a small jeep cut him off. He jacknifed and went down the bank for about 50 feet. He had his seat belt on," Fulton said.
He said his crews had a tough time pulling the tanker up the bank.
Vlassopolous insists he did nothing heroic, but Montgomery County fire officials think otherwise.
"He (the truck driver) possibly could've drowned had these people not stopped," said Pete Piringer, a spokesman for the Montgomery County Fire and Rescue Service.
Piringer identified one of the other men as Roger Francois of Germantown, and said the third rescuer was a member of the New York City Fire Dept., in the area for the holiday. However, he left before authorities could get his name.
Vlassopolous, too, got back in his vehicle and continued to work where he showered, washed his clothes twice in a failed attempt to get rid of the smell of diesel fuel, then went to work at a house fire.
"It was interesting on the way into work this morning," he said.
The Associated Press contributed to this story.