Police say threats had been made against a US newspaper before a gunman killed five people at its offices yesterday.
Smoke grenades were thrown at the Capital Gazette's building in the state of Maryland, before shots were fired at employees.
The paper's crime reporter tweeted that a gunman shot through a glass door at multiple employees.
It's reported the suspect in custody is 38 year old Jarrod Ramos.
He appears to have had a grudge against the paper after losing a defamation case in 2012.
Multiple papers report it happened after online contact he'd made with a former high school classmate turned poisonous.
The Capital Gazette reported on the threats made to the woman which prompted Ramos to take the action.
It's also reported he damaged his fingertips to avoid being identified at the scene and refused to ID himself to police.