BOSTON — Early Saturday morning, as club-goers flooded the Theater District near the Wang Theatre, downtown Boston erupted into violence, leaving one man bloodied on the pavement and police rushing in from all directions.

A packed crowd spilled into the street outside the W Hotel when a fight suddenly broke out, sending people scrambling as chaos rippled through the block. Early reports warned that a knife may have been involved, triggering an immediate surge of Boston Police cruisers into the area.

Officers arrived to find a male victim down and bleeding with a serious head injury. Medics rushed him to the hospital, where he is expected to survive.

Investigators later said the man had been punched and collapsed, striking his head on the pavement, not stabbed. The suspect vanished into the crowd before officers arrived, and no arrests had been announced as of Saturday.

Another violent flare-up in Boston’s nightlife district — and another early-morning reminder of how quickly a night out can turn dangerous.