Article continues below advertisementLiam Neeson is said to be facing one of his most frightening moments as a parent after his son Daniel Neeson underwent surgery for a rare congenital heart condition, OK! can reveal.Liam, 73, the Oscar-nominated actor known for films including Taken and Schindler's List, has been closely supporting Daniel, 29, following the procedure at Weill Cornell / NewYork-Presbyterian in New York.