retired lieutenant from the nypd standing by, also on site is james galiano, formerly with the fbi. james, when you see now what we're starting to learn about the person who did this, where is the investigation now? what are the priorities for law enforcement? >> anderson in the 21st century, every one of us have a digital footpri footprint. investigators are going back, checking records, going back and checking e-zpass, where he traveled, anything he might have put on social media. we call that digital exhaust. they're going through that exhaustively. the second thing is the human element, shoe leather, going out and knocking on doors and talking to people about what they knew about him. it's starting to paint a much better, much clearer picture of who this guy was. >> daryn, in terms of what law enforcement can learn after an incident like this.