Washington, Oct 19 (IANS): US prosecutors have decided not to charge two police officers who fired 56 unanswered rounds and killed an armed father and son in Baltimore earlier this year, a media report said.

"We have concluded that there is no legal basis to charge these officers, who appear to have prevented even further violence in Baltimore," Sun newspaper cited a statement by the prosecutors as saying on Tuesday.

The shooting took place late March when the two policemen, who were on unmarked patrol with another police officer, saw Matthew V. Wood, 43, and Kimani Johnson, 18, drive into the block near a playground and emerge from a vehicle with weapons.

The police said they believed the father and son were poised to shoot a group of people across the street, though after the gunfire police determined the duo had not fired any shots.

A third officer at the site did not fire any shot.

Tawanda Johnson, Kimani's mother, said she had not been told that prosecutors declined to charge the officers and felt upset with the decision.

"They wouldn't shoot a stray dog 56 times," she said. "They shot my son as if he meant nothing."

An autopsy showed Kimani was shot 12 times, in his body, arms, legs and head. Wood was struck eight times, also in the body, arms, legs and head.

The third officer who did not fire, Reginald Jones, told the police investigators that the officers had been in the area due to violence and drug complaints when they saw Wood open the driver's side door and emerge with a rifle.

Kimani's mother argued that Jones did not fire "says to me his life was not in jeopardy".

The dead father was found with an assault rifle loaded with 25 rounds, while Kimani had a nine mm Ruger handgun loaded with seven rounds, according to the police, adding that both of them had gun charges on their record.

The officers have already returned to full duty, though an internal review of the case is still pending, the Baltimore Sun reported.

One of the officers, Joseph Wiczulis, has been involved in two previous fatal shootings since 2010, including an incident in which he shot a man who had shot two officers.

In 2013, he also shot and killed a 25-year-old man with a handgun. He was cleared of criminal wrongdoing in both the cases.

Baltimore city officers so far have shot nine persons this year, killing four of them. Six cases remain under review by State Attorney Office.