A gunman shot and killed an imam, Maulama Akonjee, and his assistant, Thara Uddin, near a mosque in Queens, New York on Saturday (August 13).

With gunshot wounds to the head, both men died after arriving to the hospital, The New York Times reports. The New York Police Department is investigating the shooter’s motives, unsure whether it was related to the victims’ religion or race. The department detained a man yesterday but claims the person is being questioned in relation to an “unrelated” incident, Newsday reports, citing an anonymous source.

Just a day before (August 12), a woman attacked a Muslim mother and daughter in Chicago, yelling hateful slurs and spitting at them. In April, the Council on American-Islamic Relations called on New York state to increase its security measures at mosques after a 26-year-old, high on synthetic marijuana, attacked two men during an afternoon prayer service. An average of 12.6 suspected hate crimes a month occur against Muslims in the United States, according to a 2015 analysis by the Center for the Study of Hate and Extremism, published by The New York Times.

“While we do not yet know the motivation for the murders of Maulama Akonjee and Thara Uddin, we do know that our Muslim communities are in the perpetual crosshairs of bigotry,” said Mayor Bill de Blasio, in an online statement. “It remains critical that we work to bridge the divides that threaten to undermine the greatness of our city and country. Rest assured that our NYPD will bring this killer to justice.”

The funeral prayer for Akonjee and Uddin will take place later today (August 15) at 2:30 p.m. after a 1:45 p.m. news conference at the Grant Avenue Municipal Parking Field in Brooklyn.