DENVER — Armed guards, security patrols and surveillance cameras — at the Potter’s House of Denver, they are just another part of Sunday services, like prayer, psalms and sermons. Much of the security effort is hidden so it does not interfere with worship, but church leaders insist that the military-style protocols are necessary.

“We now live in an America where you must be vigilant,” the Rev. E. Christopher Hill, the church’s senior pastor, said.

The massacre last month during a Bible study at Emanuel African Methodist Episcopal Church in Charleston, S.C., has heightened anxiety among clergy members and the faithful alike, particularly in black churches. For Mr. Hill and his congregation, the event was a reminder of the importance of security measures, which they put into place years ago.

At the same time, Mr. Hill can point to violent events that captured the world’s attention and happened close to home: the 1999 shooting at Columbine High School; the 2007 shooting at New Life Church in Colorado Springs; and the 2012 shooting at an Aurora movie theater, located less than five miles from the Potter’s House church.