The National Transportation Safety Board has opened an investigation into Monday morning's bus crash in Queens that killed three people, officials said.

The crash happened around 6:20 a.m. at Northern Boulevard and Main Street in Flushing.

Sources told NY1 that a Dahlia charter bus ran a red light and slammed into a Q20 MTA bus as it was making a turn.

Sources said Henry Wdowiak, 68, was walking on the sidewalk at the time and was trapped underneath one of the buses.

One of the 14 passengers on the MTA bus, 55-year-old Gregory Liljefors, and the tour bus driver, Raymond Mong, later died at a hospital.

17 others were injured, several of them critically. Sources said the MTA driver, a 10-year-veteran, was hospitalized with non-critical injuries.

"Just shocking, you see the scene over there. It's hard to compare to anything I've seen — the sheer destruction from the impact of this collision," said Mayor Bill de Blasio.

Sources said the tour bus was traveling more than 50 miles per hour.

They also told NY1 that Mong was fired from the MTA in 2015 for a drunken driving conviction in Connecticut.

The Dahlia Group bus company, which is based in Flushing, was cited with several unsafe driving violations in the past, including five for speeding.

Last year, a Dahlia-owned bus, which a third party operated, overturned on Interstate 95 in Connecticut; one person died, and 35 people were injured.

The Monday impact in Queens spun the Q20 bus around and caused the tour bus to slam into a Kennedy Fried Chicken, sparking a fire that fire fighters later extinguished. The city buildings department was summoned, and shored up the structure to make sure it did not collapse. It is unclear if anyone was hurt from the fire.

Some local residents said the corner has long been a busy and dangerous intersection.

"Two years ago, a tour bus had killed an elderly woman, straight down on Main St," one woman said. "How many more people have to die before they can do something?"

Relatives of Wdowiak said he was walking to the subway to get to his job in the Bronx when he was hit.

His stepson Marcin Kurpiewski told NY1 that Wdowiak usually took the bus to the train, but he decided to walk this time because he was trying to live a more active lifestyle.

"He spoke with my mom about getting a little more healthy and was going to start walking to the train. That was the first day he walked, and something like this happened," Kurpiewski said. "They're saying the driver had a DUI before. Why private companies hire people with a history like that — it's just unbelievable, and this is what happens."

Liljefors lived at an apartment complex in Flushing that is not far away from the crash.

Neighbors told us he was married and was a stepfather to two children.

They said the 55-year-old worked as an overnight security guard, and was actually on his way home from the job.