Colorado Gov. John Hickenlooper knows about gun violence.
It was almost four-years ago to the date when a gunman walked into a suburban Denver movie theater and opened fire, killing 12 people and wounding dozens more.
In its aftermath, Hickenlooper, faced with intense opposition from state Republicans, helped Democrats pass some of the strictest gun-control measures in the country, which include limits on ammunition magazines and universal background checks.
The move was lauded by national Democrats, including Hillary Clinton, the party's presidential nominee. Hickenlooper, who is set to address the Democratic National Convention on Thursday, has long been a staunch ally of the former secretary of State.