Simplify the following text for a Grade 7 native English-speaking person.
Original: While Joacim was drinking with his girlfriend in a rock club he had been frequenting for over a decade , he was attacked by an unidentified person who hit him in the head with a beer glass and hastily escaped .
Simplified: While Joacim was at a rock club he had been frequenting for over a decade , he was attacked by an person who hit him in the head with a beer glass and ran away .