Wow that's awful. RIP.
According to wikipedia, the last member of Congress to die in an automobile/traffic accident while in office was Theo Ashton Thompson of Louisiana's 7th district on July 1st, 1965. He was succeeded by future political legend and living meme, Edwin Edwards.
This was something that I thought about when I heard the news, how infrequently American politicians seem to die in car crashes compared to the general population. Contrast that with the rate they die in plane crashes due to frequent charter plane usage, or seem to be involved in instances of vehicular manslaughter. I can think of several high profile instances of both, but very few where well known elected officials are killed in traffic accidents.