Paris Attacks: 3 Attackers Detonated Suicide Belts in Bataclan Concert Hall Siege

— -- Three of the attackers at Paris' Bataclan concert hall -- where hostages were held amid a series of six attacks that left at least 120 dead -- were killed when they detonated their suicide belts, according to the city's prefect.

A total of four terrorists were dead in the theater, where a witness told ABC News she heard gunmen shout "Syria!" Witnesses told French TV that they shouted "Allahu Akhbar" as they fired on the theater.

Eagles of Death Metal, an American rock band, had been performing at Bataclan Friday, and were searching for the band and crew members, according to a tweet.

"We are still currently trying to determine the safety and whereabouts of all our band and crew. Our thoughts are with all of the people involved in this tragic situation," the post said.

The brother of one of the band members said that some of the musicians managed to escape.

A witness told ABC News that she was sitting in the theater when she heard shots, which at first she thought was a stunt by the band.

French police said the gunmen first unleashed a hail of gunfire at cafes near the venue before going inside and killing more.

As police closed in, the gunmen detonated their suicide belts, police said.

In addition to the hostage situation, there were attacks at five other locations -- the Stade de France soccer stadium, where Germany was playing France, as well as four other locations in the 10th and 11th districts.

Four other terrorists were found dead and French police believe all of the attackers were killed. However, authorities were still searching for accomplices.

French President Francois Hollande and Prime Minister Manuel Valls arrived at the concert hall following the raid.

After the attacks, the Paris metro was closed and police in the city were recommending that residents avoid going out unless absolutely necessary.

Hollande said he was locking down the borders of the country and declaring a state of emergency. Hollande also called the attacks "unprecedented."

President Obama called the bloodshed an attack "on all of humanity."

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