One Shooter was Elton Simpson from Phoenix

The other shooter may have been his roomate. ABC News:

One of the suspects in the shooting in Garland, Texas, late Sunday has been identified as Elton Simpson, an Arizona man who was previously the subject of a terror investigation, according to a senior FBI official.

Overnight and today FBI agents and a bomb squad were at Simpson’s home in an apartment complex in north Phoenix where a robot is believed to be conducting an initial search of the apartment.

Officials believe Simpson is the person who sent out several Twitter messages prior to the attack on Sunday, in the last one using the hashtag #TexasAttack about half an hour before the shooting.

Local police said two suspects opened fire late Sunday outside a community center in Garland that was hosting an event displaying cartoons of the prophet Muhammad. One unarmed security guard was injured, but other security officers managed to fatally shoot both attackers before anyone else was hurt or killed.

Followers of ISIS had been sending messages about the event in Texas for more than a week, calling for attacks. One referenced January’s Charlie Hebdo massacre in France and said it was time for “brothers” in the United States to do their part.

Simpson was well known to the FBI. Five years ago he was convicted for lying to federal agents about his plans to travel to Africa, but a judge ruled the government did not adequately prove he was going to join a terror group there.

As for the second suspect, the FBI is combing through files on all of Simpson’s known associates in Phoenix and elsewhere, but so far there has been no word on the accomplice’s identity