 Masked men fired gunshots at unarmed officers and a police helicopter during this month’s riots in the English city of Birmingham, the city’s police force says.

West Midlands Police on Saturday released footage of the men firing shots during the riots on Aug. 9, and said 11 shots were fired.

Chief Constable Chris Sims called it “a concerted and organized attempt to kill or injure police officers” and appealed for people to help police catch the gunmen.

Police also said Saturday they had arrested two more suspects over the deaths of three men run down by a car in Birmingham as they protected shops from looters.

A 33-year-old man was arrested Friday and later released on bail. A 28-year-old man was detained Saturday.

The arrests bring to nine the number of people arrested over the deaths of Haroon Jahan, 20, and brothers Shazad Ali, 30, and Abdul Musavir, 31. Four have been charged with murder.

More than 1,300 people have been charged over the riots that flared in London and other English cities over four nights, and two-thirds of them have been jailed.

The flood of new inmates has brought the total prison population in England and Wales to a record 86,654, according to official figures — just 1,500 places below the countries’ operational capacity.