Police have arrested a fourth man in connection with the shooting of Detective Chief Inspector John Caldwell in Omagh on Wednesday night.
The senior PSNI officer was shot and seriously injured in front of his young son after an under-15 football session at a sports complex on the Killyclogher Road.
The injured officer remains in a critical but stable condition in hospital after surgery on his wounds.
In a statement, the PSNI said a 22-year-old man was arrested early on Friday morning in the Coalisland area.
It said the arrest was made under the Terrorism Act and the man is currently being questioned by detectives in Musgrave Serious Crime Suite in Belfast.
Three other men, aged 38, 45 and 47, were arrested on Thursday in Omagh and Coalisland. They are also being questioned at Musgrave serious crime suite.
US State Department Spokesperson Ned Price has condemned last night's attack, saying that the US stands with Northern Ireland in its "effort to ensure there is never a return to the dark days of the past".
Det Chief Inspector Caldwell is a senior policeman who has been involved in some high-profile investigations recently, including the death of Natalie McNally in Lurgan.
He was putting footballs into the boot of his car when two gunmen approached and opened fire.
The off-duty officer was hit several times in the torso as he tried to get away and was shot after he fell to the ground.
The PSNI praised a "brave" member of the public who came to his aid as the attack was taking place.
The gunmen escaped in a small black car, which was found burnt out a short time later.
The PSNI said the primary focus of the investigation was on dissident republicans, in particular the New IRA.
Tims Shiels, head coach of Omagh Harriers running club, was at the complex last night when the attack happened.
He described how "chaos unfolded" and that an assistant coach had his car "hit with bullets".
Speaking to RTÉ's Drivetime, he said: "When the shots were fired everyone went into panic mode.
"Children were running everywhere and John, after he was shot, stumbled up onto the track and he was met by some athletes from Omagh Harriers.
"I believe the first aid they administered to him on the track could have potentially saved his life."
He said that at the time of the attack "multiple groups were coming and going" as parents collected children from training and the next session was about to start.
Chief Constable Simon Byrne says the PSNI are "utterly shocked and angered by last night's brazen and calculated attack" in which Detective Chief Inspector John Caldwell was shot in Omagh, Co Tyrone | Read more: https://t.co/C06CYHMrxs pic.twitter.com/f7dCtdmipF
— RTÉ News (@rtenews) February 23, 2023
PSNI Chief Constable Simon Byrne told reporters this morning that Det Chief Inspector Caldwell is "held in the highest esteem" and "a valued and active member of his local community".
He said that the thoughts of his colleagues are with him and his family as he "fights for his life in hospital today".
Mr Byrne said it is "tragic and sad that there are some that wish to drag us back to the past".
Assistant Chief Constable Mark McEwan said there were "many other young people, children" waiting to be picked up by their parents when the attack took place.
"And those children ran for cover in sheer terror towards the centre," he said.
"It is utterly disgusting that the gunmen carried out this attempted murder in front of crowds of adults and children.
"John's own young son was with him at the time and witnessed the shooting. The trauma inflicted on this young boy is just horrific and he will never forget seeing his dad shot multiple times.
"The gunmen fired from close range in the busy sports training area, which could also quite easily have killed or seriously injured children who were present at the time of the shooting.
"Those who carried out this attack were completely reckless in their actions and they had absolutely no regard for the officer who was injured or anyone in the crowd.
"We want to hear from anyone who was in the area or who witnessed what happened to get in touch with any information that could help with our investigation."

Joint statement from five party leaders
Last night, Taoiseach Leo Varadkar called it a "grotesque act of attempted murder".
Today, he described the arrests as "significant", but said they do not know at this point who committed this crime and it was important not to jump to any conclusions.
"That's very much the security briefing that I have been given in that regard," he said.
British Prime Minister Rishi Sunak said he was "appalled by the disgraceful shooting".
Tánaiste and Minister for Foreign Affairs Micheál Martin described the shooting as "depraved and shocking".
Minister for Enterprise, Trade and Employment Simon Coveney described the attack as "a savage act by thugs who are looking to intimidate through violence".
Speaking to RTÉ's Drivetime, Mr Coveney said: "It brings us back to a different time in Northern Ireland that we never want to go back to."
Speaking on RTÉ's Morning Ireland, Sinn Féin leader Mary Lou McDonald said the shooting was diabolical and unacceptable.
In a joint statement, the Catholic and Protestant archbishops of Armagh, Eamon Martin and John McDowell, said they were united in their "condemnation of this abhorrent attack on someone serving our community".
Additional reporting PA