Accused Texas gunman was former target of FBI terror probe

A man whose social media presence was being scrutinized by federal authorities was one of two suspects in a shooting at a Texas cartoon contest featuring images of the Muslim Prophet Muhammad, and the Islamic State group on Tuesday claimed responsibility for the attack.

Simpson, of Phoenix, was arrested in 2010 after a four-year-long terror investigation. But despite an investigation that involved more than 1,500 hours of recorded conversations, including Simpson's discussions about fighting nonbelievers for Allah and plans to link up with "brothers" in Somalia, the government prosecuted him on only one minor charge -- lying to a federal agent. He faced three years of probation and $600 in fines and court fees. Simpson, described as quiet and devout, had been on the radar of law enforcement because of his social media presence, but authorities did not have an indication he was plotting an attack, said one federal official familiar with the investigation.