NEW ORLEANS — Congressional lawmakers demanded answers Wednesday about the FBI’s response to the Jan. 1 truck attack in New Orleans that killed 14 people, questioning why the bureau’s top official in the city was out of town and raising concerns about its initial, erroneous assertion that the rampage was “not a terrorist event.”

In a series of letters, Sen. Chuck Grassley, chairman of the Senate Judiciary Committee, and Sen. Ron Johnson, chairman of the Senate’s Permanent Subcommittee on Investigations, also suggested Facebook missed red flags and asked the social media company to provide a timeline of when it became aware of threatening videos Shamsud-Din Jabbar posted before he plowed a pickup through a crowd of New Year’s revelers.

Jabbar, a 42-year-old Texas native and U.S. Army veteran, professed his allegiance to the Islamic State group and an intent to harm others in a series of posts between 1:29 a.m. and 3:02 a.m., according to federal authorities.

The Bourbon Street attack began at 3:15 a.m.

— The Associated Press