STORY: Police have released chilling CCTV footage of the suspect in Monday's (March 27) mass shooting at a school in Nashville, Tennessee.The heavily-armed assailant is first seen blasting through glass doors with gunfire,and then roaming the halls of the private Christian school, pointing a semi-automatic rifle.Three children and three adult staff were killed.Police have identified the suspect as Audrey Elizabeth Hale - a resident of the Nashville area who they say used to attend The Covenant School - where the attack happened. Police chief, John Drake, said the suspect identified as transgender but provided no further clarity.He also added that the motive was not immediately known, but the suspect had drawn detailed maps of the school."And, no motive at this point? Anything discovered in the apartment or house?""No, we have a manifesto. We have some writings that we're going over that pertain to this day, the actual incident. We have a map drawn out of how this was all going to take place. There's, right now, a theory of that that we may be able to talk about later, but it's not confirmed."Drake later told NBC News that investigators believe the shooting stemmed from "some resentment" the suspect harbored "for having to go to that school" as a younger person.He said the school was singled out for attack but the individual victims were targeted at random.Reacting to the shooting in Washington, President Joe Biden urged lawmakers to do more to tackle gun violence and has called on Congress to pass an assault weapons ban.“... It's ripping our communities apart, ripping the soul of this nation. Ripping the very soul of the nation... So I call on Congress again to pass my assault weapons ban.”A Nashville church held memorial service for the victims of the massacre on Monday night.And outside the school people have started to lay flowers, balloons, and teddy bears.Local residents have spoken of their shock at the attack - just the latest in an epidemic of mass gun violence.