A man went into a Coram 7-Eleven early Monday morning, knocked out the clerk and fled on foot with the cash drawer, police say.

According to investigators, the man entered the store, took an energy drink from the refrigerator and approached the counter at the Route 112 shop around 1 a.m.

When he got close to the 53-year-old clerk, he punched him in the face, police say. The victim fell backward and cracked his head against a shelf and then the floor.

A short time later, a female customer entered the store, found the victim unconscious and called 911.

The clerk went to Stony Brook University Hospital with cuts to his head and face.

The thief made off with about $200.

"He's very dangerous because he's unpredictable," says Suffolk Detective Lt. David Teufel. "We don't know what he's going to do."