All nine bystanders injured in a shooting outside New York's Empire State Building were wounded by two police officers who had never fired their weapons before on duty, authorities have said.

Police Officer Craig Matthews fired seven times and colleague Robert Sinishtaj fired nine times at Jeffrey Johnson on a busy Friday morning in an area packed with tourists.

Johnson had earlier shot a former co-worker to death, with video from a security camera showing him pointing his pistol at police while walking away from the scene.

Based on ballistic tests and other evidence, "it appears that all nine of the victims were struck either by fragments or by bullets fired by police,'" Police Commissioner Raymond Kelly said Saturday.

Investigators were trying to piece together what caused Johnson to ambush former colleague Steve Ercolino, a vice president at the company where Johnson was laid off last year.

Police said Johnson hid behind a car and killed Ercolino with five gunshots as he arrived for work. Johnson then walked away before being shot by two police officers who confronted him moments later.

Nine bystanders were wounded in the 16-shot volley, all by stray or ricocheting police bullets. None of their injuries was life-threatening, police said.

The shooting shocked many New Yorkers out of their morning routines, with people sprawled in the streets bleeding and a tarpaulin covering a body in front of one of the world's most famous buildings.

The officers who fired were part a detail regularly assigned to patrol landmarks since the September 11 attacks on the US, officials said.

‘Not immune to violence’

Kelly said the officers who confronted Johnson had "a gun right in their face" and "responded quickly, and they responded appropriately".

"These officers, having looked at the tape myself, had absolutely no choice," he said.

Mayor Michael Bloomberg said on Friday that New York was still the safest big city in the country, on pace to have a record low number of murders this year.

"But we are not immune to the national problem of gun violence," he said of the shooting, which followed recent mass shootings at a Colorado movie theatre and a Sikh temple in Wisconsin.

Source: Al Jazeera