POLICE have urged the taxi driver who was near the gunman before his shooting spree killed one person and injured two others to come forward.

Witnesses say a woman was dragged by the hair as she tried to get into a taxi and struggled with a man before he pulled a handgun from his pocket and gunned down the trio at close range.

Police believe the cabbie saw the altercation at the corner of William St and Flinders Lane.

They also hope evidence was caught on the vehicle's security camera.

Police urged the driver to report to a depot or to call Crime Stoppers on 1800 333 000.

"We find it hard to believe he wouldn't be aware of what was going on," Inspector Glenn Weir said.