Dec. 22 (UPI) -- The two men believed to carry out the attack at a Hanukkah celebration on Bondi Beach that killed 15 people had two pipe bombs and a tennis-ball bomb that failed to detonate before the shootings and practiced shooting in advance of the attack, Australian police said.

Naveed Akram, 24, faces 15 counts of murder and injuring dozens more. His father, Sajid Akram, 50, was shot and killed by police at the scene.

Police released a fact sheet Monday saying they'd found that the pair had made two pipe bombs and a tennis ball bomb, which they threw toward the crowd. But the devices failed to detonate. Then the pair began shooting. Police said the bombs were "viable improvised explosive devices."

Before the attack, the pair hung Islamic State flags in the front and back windows of the car they drove to the beach.

The Akrams also allegedly "meticulously planned this terrorist attack for many months." They allegedly created an "ISIS inspired" video, conducted firearms training and made the explosives, police said. A video shows them "firing shotguns and moving in a tactical manner," police said.