Although the killer is known, the investigation continues into what motivated and enabled Omar Mateen to carry out the worst mass shooting in modern US history. Attorney General Loretta Lynch said in interviews Sunday on several news shows that the FBI would release a partial printed transcript of the conversations between Mateen from within the Pulse nightclub and Orlando police negotiators, the AP reports. Armed with a semi-automatic weapon, Mateen went on a bloody rampage at the club June 12 that left 49 people dead and 53 others seriously hurt. Mateen died in a hail of police gunfire after police stormed the venue. Lynch told ABC's This Week that the top goal while intensifying pressure on ISIS—the extremist group thought to have inspired Mateen—is to build a complete profile of him in order to help prevent another massacre like Orlando.
"As you can see from this investigation, we are going back and learning everything we can about this killer, about his contacts, people who may have known him or seen him," Lynch says. "And we're trying to build that profile so that we can move forward." Investigators are still interviewing witnesses, and looking to learn more about Mateen and others who knew him well, including members of his mosque. Speaking to CBS' Face the Nation, Lynch says a key goal is to determine why Mateen targeted the gay community. Federal officials tell the New York Times that so far, there's little evidence to back up earlier assertions Mateen was gay. People who knew Mateen say he could be relaxed and charming, but also aggravated and out of sync with the world. "He was just agitated about everything," says a former co-worker in the security business. "Always shaken. Always agitated. Always mad." (Read more Florida stories.)