West Ham's emotional goodbye to Upton Park turned sour tonight after fans "smashed up" the Manchester United team coach.
Bottles and other objects were hurled, smashing the coach's glass as its driver attempted to navigate past crowds on Green Street ahead of the game.
Four police officers were injured in the clashes but no-one on board was hurt.
The ugly scenes forced the game to be delayed by 45 minutes.
The FA "strongly condemned" the incidents and said it would work with both clubs and the police to investigate.
West Ham promised to issue life bans to any supporters found responsible for attacking United's coach.
Video footage from inside the coach, posted by winger Jesse Lingard, showed a number of United players shouting and laughing while lying in the aisle as objects hit the windows.
Speaking before his side's 3-2 defeat, Wayne Rooney, United captain, said: "It wasn't nice, obviously the coach was smashed up but we're here now.
"I'm, sure you'll see the images so it's not for me to say but obviously it was disappointing.
"It's a big night for West Ham with leaving the stadium but I'm sure they'll be disappointed with what the fans have done."
West Ham co-owner David Sullivan was criticised for claiming police had been "kind" to Manchester United by delaying kick off.
Sullivan blamed United for not arriving earlier instead of the fans for attacking the coach.
"I'm gravely disappointed," he told Sky Sports.
"It’s more for our supporters. They have trains and buses. We have a wonderful, wonderful show after the match. Many fans will not be able to stay for that. Man Utd should have got here at 4pm. They made the same mistake at Spurs. I’d make them kick off at 7.45pm. The police have been kind to them.”
The unfortunate episode threatened to overshadow West Ham's final ever game at Upton Park, also known as the Boleyn Ground, where they have played for 112 years.
The club will move into the Olympic Stadium in the summer.
The Football condemned the violence in a number of tweets on Tuesday night.
In a statement, West Ham United said: "It was an extraordinary night full of extraordinary moments in front of extraordinary fans - 99 per cent of whom behaved impeccably and were a credit to the Club.
"We have already had thousands of tweets and emails from fans to say how proud they were to be a part of such a special evening in West Ham's history.
"However, we are aware that there were some supporters outside the Boleyn Ground who didn't act in an appropriate way when the Manchester United team bus was damaged.
"That was not acceptable and we will work with the police to identify those responsible and ban them for life."
West Ham vice-chairman Karren Brady took to Twitter to also condemn the violent scenes.
"I, the Board and everyone at West Ham United totally condemn the unacceptable behaviour we saw outside the ground last night," Brady wrote.
"West Ham is a family Club and the vast majority of fans attended Tuesday's Final Game to respectfully say Farewell Boleyn"