The Swiss forward struck after just five minutes to silence the home crowd, finishing clinically first time to give the visitors a dream start. He then doubled the lead before half-time, a shot that flicked off Leny Yoro and crept into the corner, leaving Manchester United staring at a humiliating home defeat.
The afternoon turned darker for the hosts when Lisandro Martinez, only recently returned from two months out injured, was sent off after a VAR review for pulling Dominic Calvert-Lewin's hair. The dismissal appeared to galvanise United rather than break them, and Casemiro pulled one back with a header as Bruno Fernandes registered his 17th assist of the season — three short of the Premier League single-season record.
But Leeds held on, defending with the collective discipline that Okafor credited after the final whistle.
"I think I can score and help the team," Okafor told Sky Sports. "To every player, every staff member that is with us, a big compliment because we were fighting to the end and we deserved the three points."
On his second goal, the forward was straightforward. "I tried because if you don't try then the ball can't go in. I tried and scored my second goal so really happy about that. It brought us even more into the game and we knew we had to defend as a team."
Leeds had not won a league game at Old Trafford in 45 years. The result keeps their survival hopes alive and deals a serious blow to Manchester United's Champions League ambitions under interim manager Michael Carrick, who had won all six of his Premier League home games before Monday night.
For United, Martinez's red card will sting beyond the result. The Argentine had worked hard to return from his calf injury and lasted barely long enough to cost his side the game.
Okafor kept his composure under pressure when it mattered most. "We knew the United goal was not at the right moment so we had another 20 to 30 minutes to survive. We take this and keep looking forwards."
They took it. And Leeds may just take survival with them.