Sens. Chuck Grassley, R-Iowa., and Ron Johnson, R-Wis., on Thursday launched an investigation into the New Year's Day attacks that took place in Las Vegas and New Orleans. 

“The public deserves complete transparency and the truth regarding the New Orleans terrorist attack and the Las Vegas car explosion,” the senators said in a statement addressing the Departments of Justice (DOJ), Homeland Security (DHS), Defense (DOD) and FBI. 

“While we understand the investigation into both of these incidents is ongoing, we expect your agencies to be forthcoming and responsive to oversight requests from Congress on this very serious matter.”

On New Year's Day, a man drove a pickup truck through a crowd of people in the New Orleans French Quarter, killing 15 and injuring dozens, before opening fire on police.

The suspect was identified as 42-year-old Shamsud-Din Jabbar, a U.S. citizen and Army veteran from Texas. He died in the shootout with police, ending the carnage. He had posted five videos to his Facebook page shortly before the attack claiming his allegiance to ISIS and his intent to harm people.

On the same day, a Tesla truck caught fire and exploded outside of then-President-elect Donald Trump’s Las Vegas hotel. The cybertruck bomber was identified as a Special Forces military man.

The senators are requesting social media information from Meta about Jabbar's online activity. 

The FBI's Special Agent in Charge (SAC) in New Orleans turned out to have been on vacation that day. 

“These are major public events that a SAC should be present for. The FBI failed to note this in any of the joint briefings it provided to Congress and must provide more information,” Grassley and Johnson said.