Tennessee governor
Tennessee Gov. Bill Haslam (left) and Chattanooga Mayor Andy Berke (right) attend an interfaith vigil for the victims of the Chattanooga, Tennessee, shooting, at Olivet Baptist Church in Chattanooga July 17, 2015. Reuters/Tami Chappell

Hundreds of people gathered in Olivet Baptist Church in Chattanooga Friday evening for an interfaith memorial service to honor the four Marines killed in the shooting Thursday. U.S. Sens. Bob Corker and Lamar Alexander, as well as Gov. Bill Haslam, are expected to speak at the service.

Reporters attending the memorial service posted pictures on social media. The service started with the first speaker saying, "Folks we are Chattanooga strong," according to NBC producer James Novogrod.

Members of the Islamic community of Chattanooga encouraged Muslims in the area to forgo their regular Eid al-Fitr celebrations and attend the interfaith service.

Four Marines died when 24-year-old Mohammod Youssuf Abdulazeez opened fire Thursday morning at two military facilities in Chattanooga. Abdulazeez died in the second shooting. Department of Justice officials said in a news conference Friday that the motive of the attack is still unknown.

FBI officials said Abdulazeez was a naturalized U.S. citizen from Kuwait and attended a regional high school near the scenes of the shootings, a Marine recruitment office in a strip mall and a Marine training facility.

In a statement published Friday, Alexander said, “Heartbreaking is the only word to describe what happened in Chattanooga on Thursday. Heartbreaking for the lives who were lost, heartbreaking for the families involved, heartbreaking for the Chattanooga community. And it is heartbreaking to think that we have individuals in our society, whether they are in Charleston or Chattanooga, who think that there is some purpose in randomly taking the lives of others.”

During his remarks on Friday night's service, Chattanooga Mayor Andy Berke said that law enforcement on Thursday "thought nothing of putting their bodies between innocent lives and danger," according to reports by Novogrod, who was in the service.