Lapse in concentration
In the 11th minute, a lapse in concentration by the hosts' defence allowed Williams to pounce and give ATK the lead.
Prabir Das ran down the flank unmarked to latch onto Edu Garcia's through-ball and found Williams at the far post with a cross. The in-form forward leapt over his marker to head the ball into the net.
Krishna the star
Boosted by the opener, ATK threatened the hosts with quick counters and doubled their lead before the break. Williams delivered an excellent ball for Krishna who attacked the space behind the visitors' defence, dropped his shoulder to get past the last defender and slotted past Subhasish Roy.
Habas' team continued to pose a threat after the change of ends. Minutes into the second-half, Krishna missed a chance to score his second goal when Williams set him up in front of the goal following a two-on-one scenario. The striker sent his effort wide with an empty net in front.
The creator then almost turned scorer when Williams got to Das' pass into the box and unleashed a powerful strike that required strong hands from the goalkeeper.
NorthEast found it hard to create clear-cut opportunities. Martin Chaves' 30-yard piledriver flew harmlessly over the bar. Lalthathanga Khwalhring's cross into the box found Nikhil Kadam with just the keeper to beat, but the winger failed to control his header.
The two-goal cushion allowed ATK to drop deeper and make it harder for their opponents, whose lack of final touch meant there was no comeback in store for the home crowd.
ATK added another goal in injury time. Substitute Jobby Justin released Krishna into space behind the backline and the Fijian striker's neat finish found the net.