If he's talking about the DC Sniper, that was in 2002, so coming up on 19 years. It was also in DC, not out there. Also, one of the two people involved in that is in prison, and the other was executed in 2009.
Edit: Did some more looking, there was a series of shootings in Northern Colorado in 2015. They arrested the guy in 2018 and he still hasn't been tried due to mental health questions.
Seems to happen a lot in Colorado.