Elite troops arrived 90 minutes after the fighting began
There was confusion outside the Manawan police training academy in Lahore, Pakistan, for at least 90 minutes after the gunmen stormed the place.
Some kind of coherent response developed only later, with elite police commando units, the paramilitary rangers as well as army troops surrounding the compound.
Policemen interviewed by TV crews on the spot said the attack came during the morning parade hour when more than 800 trainees were out, all unarmed.
The militants entered the sprawling compound, apparently by scaling the boundary wall, and threw grenades at the parading trainees.
Ilyas, a police constable and eyewitness, told reporters: "We were exercising in the training ground inside the compound when we heard a blast."
"A great cloud of dust blew over us and I felt something hit my face. When I touched my face there was blood all over."
"Then I saw a man firing a Kalashnikov running towards us. He had a beard and his face was partially covered by a bandanna. Three of my colleagues fell down in the burst of firing. I just turned and ran. Thank God, I managed to get away."
Police sub-inspector Mohammad Riaz, one of the trainers who is holed up inside the school, told a TV reporter that he was trapped inside with "10 to 12 people, including policemen and recruits".
He said the attack happened when a police parade was going on around 0730. About 750 policemen were participating in the parade, he said.
"I was in my room. Suddenly there was an explosion. Then a second, and a third. Some three or four big explosions, after which firing from heavy weapons started," said Mr Riaz.
"They [probably] first threw in some grenades or rocket propelled grenades from outside the wall. The recruits started running. I saw them running. I tried to get out [of the room], but then heavy weapon fire started from all directions."
"I couldn't judge where it was coming from. All the windowpanes of the building were broken. Then we took shelter in a room and stayed there until the rescue people arrived."
Mr Riaz said the attackers were present at "three or four positions".
"Two or three men are on the second floor [of the building], some are on the third floor above, said the policeman, who said he was armed with a gun.
Some of the trainees did manage to escape, one of them with a bullet in his leg.
TV cameras peeping from over the boundary wall captured motionless images of five or six policemen, lying on the ground in the parade area.
They appeared dead, though some may have been only injured.
Some civilians were also hit and injured on the road outside the compound, apparently when the attackers fired in the direction of police security at the gate along the road.
Rescue workers have been able to take some of the injured out of the school in armoured personnel carriers.
Despite growing incidents of militant attacks across the country, the school only had peacetime security in place at the time.
Besides, some experts interviewed on TV said the training schools usually had small armouries, with old weapons not fit to counter the modern weapons of the militants.
A senior retired police official, Afzal Shigri, said it was not known whether the trainees were new recruits or trained officials on mid-service training.
He said new recruits were unlikely to challenge the attackers, but if there were any trained police officers in there, they might find a way to overcome the attackers even without any arms.
But defence analyst Lt-Gen (rtd) Talat Masood said that Pakistani policemen did not match the level of physical endurance and motivation that the militants had displayed time and again.
When the elite forces arrived 90 minutes later, they were welcomed by the crowd of spectators outside the school with loud chants of Allah-O-Akbar (God is Great).