(5 May 2015) FOR CLEAN VERSION SEE STORY NUMBER: apus030719 The maternal grandmother of Dallas shooter Nadir Soofi says her grandson was a good boy. Shirley Dromgoole spoke at her home in Eagle Lake, Texas, roughly an hour from Houston. "So kind and loving. He was very good with his little son," said Dromgoole. The Islamic State group claimed responsibility Tuesday for the assault on a Texas cartoon contest that featured images of the Prophet Muhammad, marking the first time the terror group has taken credit for an attack in the United States. But it was unclear whether the group actually directed Sunday's shooting in the Dallas suburb of Garland or if the two gunmen were inspired by the group to act on their own before they were shot and killed. Such lone wolf attacks pose a daunting challenge to law enforcement, and IS has a history of claiming responsibility for attacks in which it played no operational role, counterterrorism experts said. Federal officials identified the gunmen as Elton Simpson and Nadir Soofi, both Americans who lived in Phoenix. They were described as amicable and quiet and were sometimes seen feeding stray cats outside their apartment complex. Federal authorities had been scrutinizing Simpson's social media presence recently but had no indication he was plotting an attack, said one federal official familiar with the investigation. Federal investigators were looking for links to overseas terror groups, but as of Tuesday afternoon had not disclosed any connection or evidence to back up IS's claims of responsibility. Authorities have not revealed whether Simpson and Soofi had any contact with IS or if the group was even aware of the deliberately provocative cartoon contest in Garland. Find out more about AP Archive: http://www.aparchive.com/HowWeWork Twitter: / ap_archive Facebook: / aparchives Instagram: / apnews You can license this story through AP Archive: http://www.aparchive.com/metadata/you...