The Chief Constable of the PSNI will meet with Stormont leaders later as one of his senior officers remains fighting for his life in hospital.
A fourth man's now been arrested in connection with the attempted murder of Detective Chief Inspector John Caldwell - who was shot in Omagh on Wednesday night.
The 22 year old was detained in Coalisland in Co. Tyrone in the early hours of this morning.
Dissident republican group the New IRA is believed to be behind the attack.
Chair of the North's Police Federation - Liam Kelly - says it's a deeply unsettling time for the force.
"I mean this is a stark reality check for our officers and to the society," Kelly said.
"We're still policing probably the most dangerous part of the United Kingdom."