PSNI Chief Constable Simon Byrne has said that DCI John Caldwell is "critically ill and heavily sedated" in hospital following the attempt made on his life.
He was speaking alongside political representatives from the five main Stormont parties.
"We do not underestimate, from the point of view of the police service, how important it is that we are joined today in an act of unity from all the political parties across Northern Ireland," Mr Byrne said.
"Clearly we know from what we've done so far and from commentary from across the community, and the political spectrum, the sheer sense of outrage of this pointless and senseless attack on Detective Chief Inspector John Caldwell.
"John remains in hospital, where he is critically ill and heavily sedated.
"We have arrested a further man overnight in relation to this investigation. He is now in custody and also being questioned by detectives."
The 22-year-old was arrested in the Coalisland area in the early hours of Friday morning.
Three men aged 38, 45 and 47 also arrested in Co Tyrone remain in custody.
The leaders of the five main parties at Stormont met Mr Byrne at police headquarters in Belfast this morning to discuss the attack.
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Sinn Féin Stormont leader Michelle O'Neill emphasised the importance of unity in the wake of the attack on Mr Caldwell.
She thanked Mr Byrne for updating the parties on the progress of the investigation.
"It is so important in moments like this that we stand united," she said.
"We do stand here united as one voice in our condemnation against this horrific attack on a police officer, someone who is part of our community.
"I think that the most powerful message that we, as political leaders (can do, is) to stand with the chief constable today, to stand with the police service and say, this is not good enough. This is an attack on all of us, this is an attack on our community.
"My thoughts very much remain with the family - this is a family who are going through a trauma, these are a family who are sitting on a hospital bed, this is a son who has witnessed his father being attacked in a callous way. So, my thoughts are very, very much with John's family today."
DUP leader Sir Jeffrey Donaldson said his thoughts and prayers were with DCI Caldwell and his family as he warned the people who carried out the attack "you are not the future of this place".
"We continue to pray that DCI Caldwell will make a good recovery from the terrible injuries that he has sustained and also to say to all of those very brave men and women who each day serve our community so faithfully with great courage, that we all stand with you. You have our continued support.
"We also need to ensure that the PSNI has the resources that it needs to carry out its job effectively and we will work together as parties engaging with the government to ensure that resource is being made available to the chief constable and the PSNI, and we hope to have the opportunity to do that in the coming days.
"I would also say to the evil people who carried out this heinous attack and to their organisation - you are not the future of this place. We stand against you.
"The murder of police officers and the attempted killing of those who serve our communities in Northern Ireland is unacceptable. My cousin was the first RUC officer to be murdered by the IRA in 1970. Loyalists have also killed police officers. It was never acceptable and it is not acceptable now.
"It will not be tolerated and we stand foursquare with the police to ensure that those who have been responsible for this attack are brought to justice and that they do not dictate how this place moves forward in the future."DUP leader Sir Jeffrey Donaldson said his thoughts and prayers were with DCI John Caldwell and his family as he warned the people who carried out the attack "you are not the future of this place".
"We continue to pray that DCI Caldwell will make a good recovery from the terrible injuries that he has sustained and also to say to all of those very brave men and women who each day serve our community so faithfully with great courage, that we all stand with you. You have our continued support.
"We also need to ensure that the PSNI has the resources that it needs to carry out its job effectively and we will work together as parties engaging with the Government to ensure that resource is being made available to the chief constable and the PSNI, and we hope to have the opportunity to do that in the coming days.
"I would also say to the evil people who carried out this heinous attack and to their organisation - you are not the future of this place. We stand against you.
"The murder of police officers and the attempted killing of those who serve our communities in Northern Ireland is unacceptable. My cousin was the first RUC officer to be murdered by the IRA in 1970. Loyalists have also killed police officers. It was never acceptable and it is not acceptable now.
"It will not be tolerated and we stand foursquare with the police to ensure that those who have been responsible for this attack are brought to justice and that they do not dictate how this place moves forward in the future."
Gunmen shot Mr Caldwell in front of his young son in the attack at the Youth Sports Centre.
He ran a short distance and fell to the ground where the attackers continued to fire at him as children ran in terror to get to safety, police said.
The dissident republican group the New IRA is the “primary focus” of the PSNI’s attempted murder probe.
The attack has been condemned by political leaders across the UK and Ireland.
Mr Caldwell was coaching a youth sports team at the facility on Wednesday evening.
Mr Byrne said the presence of the five main political parties on Friday has "rippled through" the police force.
"Since we spoke yesterday, last night I had the chance to speak with John's wife and his son," he said.
"They're clearly heavily affected by what they've gone through but want to pass on their thanks both to people that rendered first aid and care at the scene, but also in terms of the outpouring of support across the community in relation to this awful outrage.
"Clearly, today we've had a chance to talk to political leaders about the pace and context of this investigation, what it means for policing and what we sense will happen in the next few days.
"We echo our thanks because it has rippled through the organisation about how important it is that we're joined by the political leaders today at this unique time to show that we stand together and call out this outrage for what it is."
