A gunman in custody is accused of killing at least eight people who had gathered at the Pittsburgh Tree of Life Synagogue, which is the latest of several houses of worship to suffer violent attacks.

Worshipers at the synagogue in Pittsburgh's Squirrel Hill neighborhood had reportedly gathered for a bris, a circumcision ceremony for a newborn boy. Several people were killed and six people were injured, including four police officers who were shot as they worked to rescue the people inside the synagogue. Local law enforcement confirmed that they did not find any evidence of explosives.

The mass shooting unfolded as many others have in recent years when houses of worship such as temples and churches become a target of violence. These types of massacres are typically investigated by federal officials as hate crimes.

Here are recent attacks in which houses of worship have been the target of gunmen in North America:

Kentucky church escapes fire
Oct. 26, 2018

On Friday, a man tried to enter a predominantly black church before killing two people in a Kroger grocery store. Video footage showed the alleged gunman, Gregory Bush, 51, tried to enter First Baptist Church in Jeffersontown, but because the service had ended and few people were left, the building was locked. Bush then is accused of heading to Kroger, where he shot two black men. Federal officials are investigating the attack as a possible hate crime.

Twenty-six killed at Sutherland Springs church
Nov. 5, 2017

Devin Patrick Kelley, 26, opened fire at First Baptist Church, killing 26 and injured 20 others. Kelly was shot twice by a civilian when he was leaving the church, and then fatally shot himself in the head.

One killed at Burnette Chapel Church of Christ in Tennessee
Sept. 24, 2017

Emanuel Kidega Samson, 25, is accused of killing a woman who was walking to her car then shot six other people when he entered the church. A note found in the car of Samson, who is black, said he was seeking revenge for a 2015 church shooting in Charleston, S.C. The church had a diverse congregation.

Six killed at Quebec City Islamic Cultural Center
Jan. 29, 2017

At a Canadian mosque where more than 50 people were worshiping, a mass shooting injured 19 people and led to six deaths. The alleged gunman, Alexandre Bissonnette, 27, was a college student who told investigators that he was troubled Canada would be welcoming more refugees and said he wanted to save people from terrorist attacks.

Nine killed at Emanuel African Methodist Episcopal Church
June 17, 2015

Dylann Roof, 23, a white supremacist, was convicted of killing nine black worshipers and has since been sentenced to death. He opened fire during a prayer service and confessed that he carried out the shooting in order to incite a race war.

Three killed at Jewish Community Center of Greater Kansas City and Village Shalom
April 13, 2014

Frazier Glenn Miller Jr., 73, was convicted of fatally shooting three people at the community center and the retirement community, and has since been sentenced to death. Miller was a Neo-Nazi with neo-pagan beliefs who had in the 1980s led the Carolina Knights, a paramilitary organization with ties to the Ku Klux Klan. Miller had discovered he had several months to live before dying of emphysema and said he planned the shooting after learning his diagnosis.

Nine killed at Waddell Buddhist temple shooting in Arizona
Aug. 9, 1991

Johnathan Doody, who was 17 at the time, and Allessandro Garcia, who was 16, were convicted of robbing and killing nine people at the Wat Promkunaram temple. The bodies of the dead were found a day later. Four other men had been charged and confessed, but they later recanted the confessions and were exonerated.