Soulja Boy Car Accident -- Other Driver Blames Rapper ... The Blow-by-Blow

The husband of the other driver in last night's Soulja Boy car crash tells TMZ -- there's no two ways about it ... the accident was all Soulja's fault.

TMZ spoke to the other driver's husband moments after last night's crash, and he tells us, he and his wife -- who's pregnant right now -- were waiting at a red light in the turning lane, when the rapper's red Bentley swerved across a double yellow line and collided with their vehicle.

The footage appears to back up the man's story.

Because the other driver is pregnant, her husband says she was taken to Cedars-Sinai hospital as a precaution following the crash.

As we reported, the other driver said Soulja Boy was driving the Bentley -- but people close to the rapper are saying it was Soulja's bodyguard behind the wheel.