
The Democratic governor defended the legislation in a press conference on Wednesday. Hickenlooper said he had found widespread support among state residents for broadening background checks, and dismissed the idea that politicians had been pressured from outside the state.
"This didn't come from the White House," Hickenlooper said.
Hickenlooper's signature came the day after the head of Colorado's Department of Corrections, Tom Clements, was shot and killed in his home, apparently after he answered a ring at his front door, authorities said.
The state has been scarred by some of the deadliest incidents of mass gun violence in recent U.S. history, including the 1999 shooting at Columbine High School and the Aurora movie theater shooting that killed 12 last July. The state's gun control bills have gained national attention since they were first proposed, drawing the ire of those who oppose any new restrictions on gun purchases or ownership.
"We're all in shock here," state Senator Greg Brophy, a Republican, said on Wednesday. "It turns out this guy who everybody thought was a moderate Democrat is actually a gun-control governor."