waiting for them, 37-year-old army veteran matthew riehl. he has a history of mental health issues. >> matt, come out! matt, come out of the room now! >> reporter: and unknown to them, a loaded ar-15 rifle. >> open the door! sheriff's office! [ gunfire ] >> shots fired, shots fired! >> my name's taylor davis. i just decided i wanted to do more for our community. >> my name's michael doyle. i know i can't change the world, but i can at least change my corner of it. >> jeff pelle. just something i wanted to do since i was little. haven't thought about doing anything else. >> dave buyer. i first got into law enforcement through the military police. i was 19 years old, thought it sounded like a good idea. >> reporter: their graveyard shift had started at 9:00 p.m. on december 30th. it was a quiet night. >> i remember kind of looking forward to that night. get in there, get it done. >> i personally had plans for a new year's eve party, let's just have a good shift, let's be safe. it was a pretty slow night up until about 3:00 a.m. >> what's going

waiting for them, 37-year-old army veteran matthew riehl. he has a history of mental health issues. >> matt, come out! matt, come out of the room now! >> reporter: and unknown to them, a loaded ar-15 rifle. >> open the door! sheriff's office! [ gunfire ] >> shots fired, shots fired!