West Ham players dived into the crowd to protect their families after they were ambushed by Dutch hooligans.
As substitute Pablo Fornals' stoppage time winner booked the Hammers' place in the Europa Conference League final, dozens of Alkmaar ultras rushed along the 'dead' zone at the front of the stand to attack the players' celebrating contingent.
The shocking scenes, a throwback to the hooligan dark ages, took the gloss off West Ham's first passage to a major final since 2006 and a first in Europe for 47 years.
More than 100 Hammers fans – mostly players' families and friends sat in the front 10 rows behind the away dugout – were subjected to unacceptable violence and Alkmaar are sure to face disciplinary sanctions from UEFA.
Former Hammers star Joe Cole told BT Sport: "AZ Alkmaar fans attacked West Ham fans where the families, friends and colleagues were sitting. Players tried to break it up. We've got to have to look at UEFA and AZ for things like that. AZ fans turned up with balaclavas throwing punches."
He added: "We had the same incidents at Frankfurt last year, and it only gets a slap on the wrist. Football's a family, we should be inclusive for everybody. The players were rightfully concerned for family, friends, kids. The men that do this type of thing are pathetic."
The ordeal served to mar a historic moment for West Ham, who booked a place in a European final for the first time in 1976.
David Moyes' side booked their place with a narrow and nervy 1-0 win over AZ, with Pablo Fornals scoring the only goal of the game in added-on time. Before that, the hosts had piled on the pressure as they looked to overturn the one-goal deficit from the first leg.
Were you involved in the incident on Thursday night? And what needs to be done to prevent this in the future? Have your say in the comments section
Nerves were shredded in the second half as the Premier League strugglers did all they could to preserve what they had. And with the time also up, Fornals sprung a wonderful counter-attack to fire into the bottom corner and spark wild scenes of celebration.
The 900-strong away end only had to wait a few more seconds before the full-time whistle, but instead of celebration, there were concerned glances towards the opposite end of the stadium. TV cameras cut away as the likes of Michail Antonio and Flynn Downes jumped the hoardings.
Speaking in his post-match press conference, Moyes said: "I can only tell you that players were involved because that was the family area. What I don't want to do in any way is blight our night, it wasn't West Ham supporters looking for trouble. Hopefully, they look into it."
Asked if his family were in the area the home supporters attacked, he added: “Yes, but you hope they will to get themselves away from it. I was on the pitch at the end and security wanted to take me inside but I wanted to make sure the players didn't get too involved.
“We'll need to wait for the dust to settle but a lot of the players were getting angry because they couldn't see if their families were OK. We will have to wait and ask the officials what really happened."
AZ Alkmaar boss Pascal Jensen strongly condemned his own fans and said he was ashamed of the minority that attempted to ruin the occasion. “I feel a bit ashamed that those scenes happened in our stadium. It shouldn't be happening – the game didn't go as we hoped, but you have to stay in control of your emotions.”
“There was no need for it," Carlton Cole added. "West Ham have come here and done a job, they haven’t disrespected them in any form. Obviously, when the goal goes in from Fornals, everyone’s elated. You can’t suppress your feelings.
“The families are over there…they aren’t going to be with the away fans. Sometimes you’ve got to understand that. These are the same fans - in black balaclavas - that were outside the players’ hotel letting off fireworks last night…what are they doing?"
West Ham's goal scorer Fornals told reporters: “I didn’t see a lot because I don’t have anyone here watching so when the referee whistled the end, I just fell to the floor. After that I went inside to keep the guys in, we don’t need that. Obviously, I was really concerned about how the family of my team-mates and the West Ham family are. Now the police can do their job and find out who did it.”
He added: “It’s not great when you are in that beautiful moment and other people are trying to use violence against you. But we can’t do anything but help the police and help them find out who did this.”
Robin van Persie was also on punditry duty and was asked whether he understood why West Ham players intervened: “Of course I do. From the point of view of the West Ham fans, they are allowed to be happy and celebrate. This shouldn’t have happened and it’s a big shame.”
Joe and Carlton Cole revealed they also went over to the area of the stadium that was engulfed in trouble. “Yeah, we’ve got family and friends over there,” Joe explained. “In the modern game, the amount of data we have, the cameras…find these people and ban them!
“I was talking to a few of my pals about bringing kids to the final, then you start second-guessing it after seeing scenes like that.”
