GENEVA - Syria's crackdown on anti-government protesters may constitute crimes against humanity, a UN investigative team said on Thursday, adding it had evidence implicating 50 people at various levels of government who could be prosecuted. Syrian forces fired on peaceful protesters throughout the country, often at short range and without warning, killing at least 1,900 civilians, including children, investigators said in a report. Their wounds were "consistent with an apparent shoot-to-kill policy," it said. Some were reportedly finished off with knives. Tanks, grenades, snipers, heavy machine guns and helicopters have been used in the assault aimed at quashing opposition to the rule of President Bashar Assad, they said in a report to the UN Human Rights Council. The 47-member Geneva forum is to hold a special session on Syria on Monday.