Texas Shooting Suspect Elton Simpson's Private Messages: 'The Noose Is Tightening'

ISIS calls would-be killers "soldiers of the Caliphate."

— -- Private Twitter messages written by one of the suspects in the weeks before the Garland, Texas shooting Sunday reveal a man who had turned against his country.

On April 10 he wrote, "Time is short."

Less than two weeks later he referenced the Mohammad drawing contest -- the site of Sunday's attack -- saying, "When will they ever learn?"

"Bring your passport. If you have $4,000, that's enough to travel with," he wrote on April 10.

But his plans were disrupted when the FBI in San Diego and Minneapolis arrested some people he wanted to go with him, he said.

Both Simpson and his purported accomplice in the Garland shooting, Nadir Soofi, were killed shortly after they opened fire outside an event that was displaying cartoons of the Prophet Mohammad. Though armed with assault weapons and some kind of body armor, the pair was killed by a traffic policeman using a service pistol before they could take any lives, local police said.

The families of both shooting suspects said they were shocked and dismayed by what Simpson and Soofi had done.

"My son made a bad choice," Simpson's father, Dunston, told ABC News Monday. "We are Americans and we believe in America. What my son did reflects very badly on my family."

Overnight ISIS released a statement calling the men "soldiers of the caliphate" and promised worse attacks were to come, though so far there is no evidence the failed Garland attack was actually directed by the terror group.