Five people were killed after a gunman opened fire in the newsroom of a Maryland newspaper.

Thursday's attack at the Capital Gazette newspaper in Maryland is the deadliest day for journalism in America since 9/11.

The attacker walked into the office of Capital Gazette with smoke grenades and a shotgun in what police called a "targeted attack". 

The identities of the victims were released on Thursday night. Rob Hiaasen, Gerald Fischman, Wendi Winters, and John McNamara were editors, and Rebecca Smith was an ad sales assistant for the paper.

The suspect has not been named by US police, but multiple news outlets have identified him as Jarrod Ramos, a 38-year-old man who had previously sued the newspaper for defamation in 2012.

Ramos is in custody and policy are investigating his home.