What to Know Maryland State Police motorcycles blocked traffic at I-70 and the I-270 ramp to assist a congressional motorcade, state police said.

Two dump trucks and the SUV had stopped when another dump truck rear-ended the SUV, triggering a fatal chain reaction crash.

Senate Democrats are holding a retreat in Shepherdstown, about 70 miles from Washington, a spokesman for Senator Bernie Sanders said.

The driver of an SUV who stopped to allow a congressional motorcade to pass died in a fiery crash involving three dump trucks Wednesday morning, Maryland State Police said.

State police motorcycles blocked traffic at Interstate 70 and the Interstate 270 ramp in Frederick to assist a U.S. Capitol Police motorcade, state police spokesperson Elena Russo said.

Two dump trucks and the SUV traveling westbound on I-70 stopped for the motorcade when when another dump truck rear-ended the SUV after 9 a.m., triggering a chain reaction crash with the other dump trucks ahead of it.

The crash caused an explosion for unknown reasons, and two dump trucks and the SUV became engulfed in flames.

The only person in the SUV, 46-year-old Jacob Jackson of Gaithersburg, Maryland, died. The victim's identity remains unconfirmed.

Fire and EMS took the drivers of two of the dump trucks to Frederick Memorial Hospital. The third refused medical treatment.

The motorcade was traveling from Washington to Shepherdstown, West Virginia, said Eva Malecki, of U.S. Capitol Police. No motorcade vehicles were involved in the crash, she said.

Senate Democrats are holding a retreat in Shepherdstown, about 70 miles from Washington, a spokesman for Sen. Bernie Sanders said.

Sens. Ben Cardin and Chris Van Hollen, both Democrats from Maryland offered condolences to the victim's family in a joint statement. They traveled to the retreat in their own vehicles and were not part of the motorcade.

The crash disabled all four vehicles, state police said.

The crash closed westbound I-70 and northbound off-ramp lanes of I-270, the Maryland State Highway Administration said on its website. All lanes reopened, and the investigation continues.