A monsignor at St. Rose of Lima Roman Catholic Church in Connecticut said a telephone caller told him, “I’m coming to kill, I’m coming to kill.”
The Newtown church had been the site of ongoing vigils after the Friday morning massacre at Sandy Hook Elementary School.
The New York Times reported on the threat from a live stream from Ora.TV.
The church was evacuated during Sunday Mass after it received a bomb threat.
It is unclear whether there was another threat, aside from the caller, that spurred the evacuation.
Police gave the "all clear" sign at the church shortly after the evacuation, according to NBC News.
Deborah Metz, a Trumbull police officer on the scene, gave the all-clear after an hour in which armed police in SWAT gear searched the church and adjacent buildings.
The evacuation unnerved worshippers in the wake of the worst shooting of school-age children in U.S. history.
Police say the church will be on lockdown for the rest of the day.
Shooter Adam Lanza, his mother and eight of the child victims attended St. Rose of Lima. It is a Roman Catholic Church with an adjacent school, which Lanza attended briefly.