Three boys aged eight, 10 and 11 have died after plunging into an icy lake when the ice broke.
A fourth boy aged six is in a critical condition.
The lads had been playing on ice in Babbs Mill Park, Kingshurst, West Midlands.
Police officers and passers-by desperately tried to bring the boys to safety.
One police punched through the ice to try to grab the four.
Richard Stanton, West Midlands Police the area commander, feared there was little chance of finding anyone else alive.
He said: “The specialist medical advice we have been given on the scene, given the temperature of the water, given the age of those who entered the water and the amount of time they have been in there, this would no longer be a search and rescue operation.”
Superintendent Richard Harris said all the police at the same entered the water with no regard for safety or specialist equipment.
“Our thoughts are with the family and friends of the boys at this deeply devastating time.
“We’ll have specialist officers offering them as much support as we can.
“Searches of the lake are continuing as we seek to establish exactly what happened and if anyone else fell into the water.
“We understand how distressing this is for the families and the wider community.”
Specialist firefighters eventually reached the children and brought them ashore.
Temperatures dropped to 1C (34F) in the area at the time of the incident, falling to -3C (26F) overnight.
A fire service spokesman said:
“The lake can look picturesque but can be lethal.
“Please help avoid this from happening again.”
Prime Minister Rishi Sunak has said his thoughts were with the families.
He spoke to Meriden MP Saqib Bhatti, who was visiting the scene.
Mr Bhatti praised the emergency services for their efforts.
He said: “In these conditions not to worry about your own safety and just to go after those children is heroic.”
Residents went to the scene with hot drinks for the rescuers.
One told how he had heard the sirens and saw people running down to the site.
He grabbed his jacket and ran down to see if he could help.
“It’s shocking, I haven’t really been able to sleep to be honest.”