"Incendiary devices" were found at a Jehovah’s Witness hall after the apparent murder-suicide of a married couple there on Christmas Day, Colorado police said.
"An adult female was shot and killed by an adult male, who then shot and killed himself," police said in a statement Sunday.
Police in Thornton, which is about 10 miles north of Denver, said the two were former members of the congregation.
Officers were originally called to the scene after reports of a fire.
The devices were rendered safe, police said, adding there were no additional suspects.
"No other people were injured as a result of this incident," they said.
The Adams County Coroner's Office will release the identities of those killed later, police added.
"This kind of violence is always shocking but particularly on Christmas Day," Thornton Mayor Jan Kulmann said in a statement on Twitter.
If you or someone you know is in crisis, call 988 to reach the Suicide and Crisis Lifeline. You can also call the network, previously known as the National Suicide Prevention Lifeline, at 800-273-8255, text HOME to 741741 or visit SpeakingOfSuicide.com/resources for additional resources.