SYDNEY, Dec 15 - Australian police said on Monday that the alleged offenders behind an attack at a Jewish celebration in ?Sydney's ?Bondi beach that killed 15 people, were a ?father and son duo. One of the gunmen was also killed, bringing the death ?toll to ?16. It was the country's worst gun attack in about 30 years. The father, a 50-year old, was killed at the scene while his 24-year-old ?son was in critical condition in the hospital, the police said in the ?press conference on Monday. Witnesses said ?the shooting at the famed beach, which was packed on...