"I knew that it was going for a six from the moment it had crossed the 30-yard circle."
He was calm and gripped the bat normally, not clutching it tight as many of us do when facing that sort of situation, even in our backyards.
He looked at the ball fly out of Isuru Udana's hand, picked up the length on reflex and flicked it over square leg. All in one motion.
"I was trying to be as calm as possible," Mahmudullah told ESPNcricinfo. "My gloves were ruined after diving to take two off the fourth ball. I called for replacement gloves and some water. I think I steadied myself in that little break."
It was Bangladesh's Sharjah 1986 moment, coming in a knockout game against subcontinental neighbours who are becoming their arch-rivals.
Mahmudullah had been in such situations before: as a batsman, taking Bangladesh to a two-wicket victory over England with an over to spare in the 2011 World Cup; and as a bowler, twice helping Khulna Titans to last-over wins.
"A lot of negativity swims in your head in these moments. I have had some experience of being unable to overcome these situations. So my only prayer to Allah was to be on the winning side," he said.
Given the angry scenes leading up to the last three balls of the Colombo match, it was understandable that Mahmudullah was unsettled.
An argument had erupted between Bangladesh's substitute players and the Sri Lankan fielders while Mahmudullah was pleading with the umpires to call the second ball of the over a no-ball. Then, as a sign of protest, Shakib Al Hasan, the Bangladesh captain, standing near the boundary rope, gestured to his batsmen to come off the field.
"I started off as a bowling allrounder. I batted at No. 7 or 8 and bowled some overs. In 2014, when Hathurusingha came, I got the promotion to No. 4 and I felt I have to grab this opportunity with both hands"
"The first ball was a proper bouncer," Mahmudullah said, recalling the final over of the game. "I saw the [square] leg umpire signal the one bouncer, and I told Mustafizur [Rahman, his batting partner] that he won't be getting another bouncer next ball. He might bowl him a short one up to his waist. I told him, 'You just be ready for a length ball or yorker. We have to take a run this ball, no matter what happens'.
"[Udana] bowled another bouncer, which went slightly higher than the previous delivery. Leg umpire called a no-ball as we tried to take the bye. Mustafizur got run out at the other end. [Kusal] Perera spoke to the main umpire, who then discussed something with the leg umpire. I was told that since the main umpire didn't signal a bouncer in the first ball, this won't be a no-ball. I said that since it was signalled a bouncer in the first ball and then the second ball was given a no-ball, why wouldn't it be a no-ball?
"What happened next was in the heat of moment. It was unexpected. But we really wanted the game to end properly. I think the break helped us in some way. We found some breathing space."
What stood out in the chaos was Mahmudullah's calm demeanour.
"I think it is in my make-up, both personal and professional. It helps in my game. You are playing for your country in front of a large audience, both at the ground and back home. You think of expectations from the team, yourself and the family. It is pleasing to win a game for Bangladesh."
His six off the penultimate ball silenced the stadium. "It was certainly a new experience [to see the crowd go quiet after we won]. They were stunned. But what goes around comes around. We copped the other side in the final."
That other side was of course Dinesh Karthik's last-ball six that silenced Bangladesh amid a roaring Colombo crowd that emphatically backed India in the final.
"I sank to my knees. It expressed everything I felt," Mahmudullah said.
The last 12 months have been a rollercoaster for him, bookended by events in Colombo. In March 2017, he was dropped for Bangladesh's 100th Test, at the P Sara, having scored only one half-century in his previous 13 innings. However, a few months later, he played the innings of his life in a Champions Trophy match against New Zealand to take Bangladesh to their first semi-final in a major ICC tournament.
He was kept out of the Test side for the home series against Australia in August-September because coach Chandika Hathurusingha wanted continuity in the team. But Bangladesh missed his experience in the 1-1 drawn series, and he was recalled for the tour of South Africa, where he was one of only two Bangladesh batsmen to make some runs.
"I try to take positives out of every situation. I felt that perhaps I went through such a phase because I lacked in certain areas. If I don't perform well, I have to accept what comes my way.
"I think that particular time helped me find myself better and return in better shape. I worked harder, physically and mentally. I spoke to everyone close to me, like Mashrafe bhai [Mortaza] and coach Hathurusingha, to get myself back on track.
"Personally [in the South Africa series], I should have played bigger innings, which would have helped my team. It is disappointing somewhat, but I think the tour gave me confidence in my Test batting."
Mahmudullah said that he looks at Virat Kohli as an example to venture out of his comfort zone. "He is a different Virat Kohli now. He dominates everyone. I have seen him train a few times. His work ethic is outstanding, as it shows how you can improve as a cricketer."
The first time Mahmudullah stepped out of his comfort zone was in January 2016, when he was asked to be Bangladesh's finisher in T20Is. It was a bold move from Hathurusingha, since Mahmudullah had a lowly strike rate of 103. He had hit only 15 sixes in 32 innings, but his ODI form was in his favour, with two hundreds in the 2015 World Cup.
To fit the finisher's role he had to transform his mentality in a matter of weeks during a training camp in Khulna. "A lot of the credit goes to Hathu. I was batting at No. 4 in ODIs. Hathu told me to prepare myself to bat at No. 6. I wasn't the type of batsman who could charge bowlers from the first ball. I had to change a lot of things.
"I worked harder, physically and mentally. I spoke to everyone close to me, like Mashrafe bhai and coach Hathurusingha, to get myself back on track"
"I decided to do something different in that Khulna camp. I took it as a challenge to cross my threshold and did day-by-day improvement. If you have the concentration to correct yourself in the proper way, you will get success."
Mahmudullah decided that most of his shots from Tests and ODIs could be incorporated into his T20 game, only needing the adjustment of going after every ball. In particular, he worked hard on his loft over cover, which has now become his signature shot.
"Batting on a granite slab was quite helpful. Since in a game situation I have to connect from the first ball, I try to keep that in mind in training."
He found instant success and quickly became a dependable big hitter. In 28 innings since becoming a finisher, he has a strike rate of 134.36 and has hit 47 fours and 20 sixes.
A few of Bangladesh's top cricketers have had to make major changes in their game. Tamim Iqbal had to tweak his on-side game early in his career; Shakib and Mushfiqur Rahim have bounced back from dips in form; Mortaza dealt with several injuries and turned from being a tearaway quick to a medium-pacer; Mohammad Ashraful never quite turned his talent into consistency; while others like Habibul Bashar or Aminul Islam based their international career on what they learned from domestic cricket.
But Mahmudullah had to make two major comebacks, negotiate with several changes in his batting position in Tests and ODIs, and in his ninth year in international cricket, reinvent himself as a T20 hitter.
"I started off as a bowling allrounder when I made my ODI debut in 2007. I batted at No. 7 or 8 and bowled some overs. In 2014, when Hathurusingha came, I got the promotion to No. 4 and I felt that I have to grab this opportunity with both hands.
"The shift in the batting position was a lot of work. Then I was given the finisher's role in T20s in 2016. I had to shift the gear one more time."
In a country where risky batting is discouraged, which has hampered the growth of big hitters, Mahmudullah is a great example of how hard work, sharp thinking and guts can help a batsman grow in any format. His tenacity should serve as a reminder to players who have given up on the idea of returning to the national team. Mahmudullah will certainly be remembered for his heroics in the Nidahas Trophy, but how he got to this point as a T20 batsman is the more remarkable story.
Mohammad Isam is ESPNcricinfo's Bangladesh correspondent. @isam84