This follows a similar attack in May on another UN-run summer camp.This wasn't the first attack of this kind. Another attack along these lines occurred in May at another UNRWA-operated summer camp.
Some militants view the UN as a symbol of the West and claim that the summer camps allow boys and girls to mix freely - something that the UN denies.
The attackers tied up the guard at the camp in central Gaza before setting fire to chairs, tables, easels and other equipment.
The UN says about 25 armed men attacked the beach camp in the middle of Sunday night.
You can't blame this on Israel either. Hamas decided to rob one of Gaza's banks because it was hard up for money to fund Hamas operations. The money had been frozen by the rival group Fatah, which controls the funds:
Hamas security forces seized $16,000 on Sunday from a Gaza bank that had frozen the funds as part of an anti-money laundering campaign launched by the West Bank-based Palestine Monetary Authority (PMA).
A senior official at the Palestine Islamic Bank said Hamas police took the cash from tellers at gunpoint. No one was hurt in the incident. Hamas officials had no immediate comment.
The bank said the money was in an account of an Islamic charity that had been frozen by the PMA, which acts as a central bank for President Mahmoud Abbas' Palestinian Authority, Hamas' rival.
The account was frozen after Hamas, which won a Palestinian parliamentary election in 2006 and took control of the Gaza Strip in 2007, brought in its own people to manage the charity.
It was the second time Hamas seized money from a private Palestinian bank this year. In March, its forces took $400,000 from a bank in defiance of the PMA, raising concerns among bankers over the safety of operating in Gaza.