Federal investigators Sunday took the first steps in trying to figure out exactly how an Atlanta police helicopter got tangled up in power lines before it crashed. But it may take several months before those investigators find all of the answers.

Witnesses have told the National Transportation Safety Board the helicopter clipped the top of a power line pole and its support cables before falling to the ground Saturday night. The chopper burst into flames near the intersection of Martin Luther King Jr. and Hamilton E. Holmes drives. Officers Richard J. Halford, 48, and Shawn A. Smiley, 40, are dead.

“I heard a boom like a bomb, and I looked out the window and flames were everywhere,” Rebecca Horne – who lives just a short walk from the crash site -- told Channel 2 Action News. “I looked out the window and flames were everywhere.”

Ralph Hicks, investigator in charge for the NTSB, says a preliminary report could be ready by the end of the week. But usually these investigators take six to nine months.

The two officers were using the helicopter to search for a 9-year-old boy that had run away from home. He was later found safe.

“I just want to tell their families I am so sorry and all I can do is cry,” the boy’s mother Amire Shakir Fulford told Channel 2 Action News.

The flag at Atlanta police headquarters sits at half-staff. Mourners visited the police station and the crash site all day Sunday to pay their respects.  A make shift memorial has started to grow.

“The loss of an officer is probably the most difficult thing a chief of police to have to deal with,” Atlanta Police Chief George Turner said. “Magnify that twice and it's a very difficult time for not just me but the entire Atlanta police department.”

Halford, of Lithia Springs, had been with APD since 1986. He joined the air unit 16 years ago as a pilot. Atlanta police say he is survived by his former wife, and a 21-year-old daughter.

Smiley, of Lithonia, joined the department two years ago. He became a tactical flight officer earlier this year. He leaves behind a wife and three children, ages 5, 7, and 9.

Wells Fargo bank will start taking donations at noon on Monday for trust funds that have been created to benefit the officers’ families.

“We mourn these two brave men and offer our deepest condolences to their families and loved ones,” Reed said in an emailed statement. “We also pause to extend our sympathy to the men and women of the police department who place their lives in harm’s way every day to keep our city safe, and who especially feel the pain of this loss.”

Funeral arrangements are pending.

No one on the ground was injured in the crash.

The aircraft was light helicopter manufactured by Hughes, Hicks said. It was flying in a northwest direction when it hit the power pole. Parts of the helicopter were still intact when they were removed.

These two officers are the second and third APD officers to die in the line of duty this year. In January, Senior Officer Gail Thomas died was arriving at a crash scene to help a fellow officer when she was struck by a drunk driver.