One likely scenario is an Islamist agent making such a hit look like an American leftist's work. Sew chaos. That would be the goal of any remaining Evil Axis agents. Getting us to hate each other is their job #1. So far it's working, unfortunately.
THE BALLOONIST
A woman in a hot air balloon realized she was lost. She lowered altitude and spotted a man in a boat below. She shouted to him,
"Excuse me, can you help me? I promised a friend I would meet him an hour ago, but I don't know where I am."
The man in the boat consulted his portable GPS and replied, "You're in a hot air balloon approximately 30 feet above a ground elevation of 2346 feet above sea level. You are 31 degrees, 14.97 minutes north latitude and 100 degrees, 49.09 minutes west longitude."
She rolled her eyes and said, "You must be a Republican.."
"I am," replied the man. "How did you know?"
"Well," answered the balloonist, "everything you told me is technically correct ... I have no idea what to make of your information . . . and I'm still lost. Frankly, you've not been much help to me."
The man smiled and responded, "You must be a Democrat."
"I am," replied the balloonist. "How did you know?"
"Well," said the man, "you don't know where you are or where you are going. You've risen to where you are, due to a large quantity of hot air... You made a promise that you have no idea how to keep . . . and you expect me to solve your problem.. . . You're in exactly the same position you were in before we met. . . but somehow, now it's my fault."