Abu Musa Al-Ash`ari (may Allah be pleased with him) reported that the Prophet (peace and blessings be upon him) said: "If a child passes away, Allah says to His angels, ‘Did you take the soul of My servant’s child?’ And the angels would say, ‘Yes.’ Thereupon Allah would say to them, ‘Did you take away the apple of his eye?’. ‘Yes,’ the angels would reply. Then Allah asks them, ‘And what did my servant say?’ And the angels would say, ‘He has thanked You and committed all his affairs to You.’ Then Allah would say, ‘Then build a house in Paradise for My servant and name it the House of Thankfulness'" (Reported by At-Tirmidhi).

Responding to the question, Dr. Rif`at Fawzi, former professor of Shari`ah at Cairo University, states the following:

Those children who die before the age of puberty are considered martyrs. They will, in sha’ Allah, lead their parents to Paradise. The Prophet (peace and blessings be upon him) is reported to have said, "If a (Muslim) woman’s three children die, they will be a protection for her from Hell." A woman asked him, “And what if two of her children die?” He replied, "And (even) if two of her children die."

Having said this, I ask the parents who lost their children in that tragic event to exercise remarkable patience, for if they are truly patient they will be generously rewarded by Allah.

May Allah shower all those who died with His mercy, aameen.