John Caldwell made his first public appearance since the shooting at Hillsborough Castle on Wednesday
Four people arrested as part of the investigation into the attempted murder of senior detective John Caldwell have been released.
The two men, aged 34 and 21, and two women, aged 52 and 34, were among 11 people arrested in County Tyrone on Friday.
They have been released pending a report to the Public Prosecution Service.
The others, seven men aged between 21 and 72, remain in custody.
Det Ch Insp Caldwell was shot while putting footballs into his car at a sports complex in Omagh on 22 February.
Officers believe the dissident republican group the New IRA may have acted with an organised crime gang to carry out the attack, which left the detective chief inspector with life-changing injuries.
On Friday, the police released new CCTV footage and photographs of vehicles they believe were used in the attack.
The CCTV shows footage of a number of cars used by the gunmen on the day of the attack
The police said three vehicles they believed were used by the gunmen were spotted travelling in convoy on the Drumnakilly Road in the direction of Omagh in the hours before the attack.
Det Ch Insp Caldwell appeared at Hillsborough Castle on Wednesday where he had an audience with the King.
It was the first time he had appeared at a public event since he was discharged from hospital.
Who is detective John Caldwell?
He is one of the best-known detectives in the Police Service of Northern Ireland, often fronting press conferences on major inquiries during his 26-year career.
Mr Caldwell investigated the 2011 murder of his colleague Ronan Kerr by dissident republicans.
He was aware his investigations relating to dissident republican attacks – including the killing of Lyra McKee in 2019 – made him a high-profile target.
In January, he spoke to reporters after the killing of Shane Whitla, a 39-year-old father of four who was shot a number of times in the town of Lurgan in County Armagh.
He was also the initial lead detective investigating the killing of Natalie McNally in Lurgan, and he was involved in investigating the murder of Mark Lovell, 58, who was shot a number of times at close range in his car in Newry in County Down on 1 December.
He had received a number of threats in the past, BBC News NI understands.
