"In the Congress, some definite evidence proposed by a retired pentagon member proving Saudi Arabia’s direct role in other terrorist operations including Rafic Hariri’s assassination. I’ll firmly back the legislation" , Grassley said.
Rafic Hariri the former Prime Minister of Lebanon, was killed along with 21 others in an explosion in Beirut on 14 February 2005. During that time, media especially the Israeli daily Ha'aretz condemned Lebanese militia Hezbollah and made them responsible for the assassination.
Along with submitting 9/11 bill allowing families of victims to sue Saudi Arabia, voices came out that Saudi Arabia was also involved in Rafic Hariri’s assassination planned by Israel in 2005 and also it had role in promoting terrorism in the United states and Europe. This is why the senators are vowing to decisively support 9/11 bill and override President Obama’s veto. source