A small tip given to a waitress as a joke may have triggered a brutal attack with a weapon described as a hatchet, San Diego Police said.

A man was hit in the head by a hatchet or some other blunt metal object at 5:46 p.m. behind River Sports Bar Casino on El Cajon Boulevard, near 55th Street, police said.

Before the attack, the victim bought multiple shots for everyone at the bar, witnesses told NBC 7. When he gave the waitress a small tip, she threw it back at him, the witnesses said.

That victim then threw a wad of cash at the waitress and walked out of the bar, witnesses said.

When the victim got outside, two men confronted him and then attacked him, police said. The suspects got into a black BMW and took off.

The victim also left the scene before police arrived.

Residents in the area told NBC 7 they are disturbed by the violence and the impact it has had on the community.

"It affects all of us. It brings down the economy because people don't want to come to the community. Even though it doesn't happen every day, isolated incidents like this do affect the long-term economy in just about every community," said Maurize Rios, a El Cerrito resident.