In front of a stunned capacity crowd of 25,000 in Dhaka, the home side's batting imploded and they were all out in just 18.5 overs - sparking angry scenes from supporters who hurled placards from the stands.
The West Indies team bus was also stoned as they made their way back to the hotel later. "A couple of fans threw stones, two hit the window and it just broke. No one was hurt and we are safe," A team spokesman told Reuters.
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The West Indies opener Chris Gayle tweeted from the bus: "Bangladesh stoning our bus!!! Freaking glass Break!!! This is crap, can't believe ... what next bullets!!
"This is ridiculous!!! Damn!!! W Cup with so many security an this happen!! Big Joke!!! Trust me I'm not keen here!!! ... players lay flat!!"
A Bangladesh police officer said that the fans had thought the bus was carrying the home team after the Caribbean side romped to their second win of the tournament in just 12.2 overs, with Gayle making an unbeaten 37.
Spinner Sulieman Benn grabbed 4-18 and fast bowlers Kemar Roach and Darren Sammy claimed three wickets each as Bangladesh fell well short of their previous one-day low of 74, notching the fourth lowest score in World Cup history.
Junaid Siddique and Mohammad Ashraful were the only two batsmen who made it into double figures in a match that could prove pivotal to quarter-final hopes with India, South Africa and England also in Group B.
The West Indies skipper Sammy praised teammate Chris Gayle for a motivational speech that inspired his side.
"It was a brilliant performance by my teammates. Chris Gayle wasn't feeling well today but I thought he came out and showed how committed he is to the cause," he said.
"He said 'do not take Bangladesh lightly'. We were a little flat in the warm-up and he didn't like that so he encouraged us to go out there and remember Bangladesh would be coming hard at us."
"We've always fancied ourselves but it's up to us to go out there and play competitive and consistent cricket," he added.
Shakib Al Hasan, his counterpart, was at a loss to explain his team's disastrous showing, adding that he understood the fans' frustrations.
"We have a lot of things to work on now. We have to sit down and think about it but hopefully we will come back strongly."
He said reaching the quarter-finals was still possible after one win out of three so far, with the game against England in Chittagong now a "must-win".
The home team lost hard-hitting opener Tamim Iqbal off the third ball of the match when the left-hander attemped a lofty cover drive off Roach and edged a catch to Sammy at second slip.
Sammy, who handed the new ball to left-armer Benn for one over before coming on himself, forced Imrul Kayes to edge a catch to wicket-keeper Devon Thomas with his third delivery.
In his next over, Sammy removed Mushfiqur Rahim for no score, the young batsman flicking a catch to Ramnaresh Sarwan at short-mid-wicket.
Junaid Siddique hit a fluent 25 with four boundaries when he fell leg-before to Roach, a decision that was referred to TV umpire Asad Rauf.
Benn, who replaced Roach after the fast bowler's five-over spell that cost just 18 runs for two wickets, bowled Shakib with his second ball.
Sammy earned another success in his sixth over, the 14th of the innings, when Raqibul Hasan drove a slower ball to point where the towering Kieron Pollard took a low catch.
Roach, replacing Sammy for his second spell, struck with his first ball when former captain Mohammad Ashraful edged a catch to the wicket-keeper after making 11.
Benn then took the last two wickets in three balls to terminate the Bangladesh innings in quick time.
Tamim Iqbal c Sammy b Roach 0
Imrul Kayes c Thomas b Sammy 5
Junaid Siddique lbw b Roach 25
Mushfiqur Rahim c Sarwan b Sammy 0
Shakib Al Hasan b Benn 8
Raqibul Hasan c Pollard b Sammy 4
Mohammad Ashraful c Thomas b Roach 11
Naeem Islam c Thomas b Benn 1
Shafiul Islam c Pollard b Benn 0
Abdur Razzak not out 2
Rubel Hossain b Benn 0
Extras: (nb1, w1) 2
Total: (all out, 18.5 overs) 58
Fall of wickets: 1-0 (Tamim), 2-16 (Kayes), 3-25 (Rahim), 4-36 (Siddique), 5-41 (Shakib), 6-51 (Raqibul), 7-56 (Naeem), 8-56 (Ashraful), 9-58 (Shafiul), 10-58 (Rubel)
Bowling: Roach 6-0-19-3 (nb1, w1), Benn 5.5-2-18-4, Sammy 7-0-21-3
D Smith b Naeem 6
C Gayle not out 37
D Bravo not out 9
Extras: (b2, w5) 7
Total (for one wicket, 12.2 overs) 59
Did not bat: Darren Sammy, Ramnaresh Sarwan, Shivnarine Chanderpaul, Kieron Pollard, Devon Thomas, Sulieman Benn, Nikita Miller, Kemar Roach
Fall of wicket: 1-29 (Smith)
Bowling: Shafiul 2-0-11-0, Naeem 6-1-14-1 (w1), Rubel 1-0-12-0, Razzak 1-0-8-0 (w4), Ashraful 2-0-11-0, Shakib 0.2-0-1-0
RESULT: West Indies won by nine wickets
Lowest World Cup totals
Canada 36 v Sri Lanka Paarl 19 Feb 2003
Canada 45 v England Manchester 13 Jun 1979
Namibia 45 v Australia Potchefstroom 27 Feb 2003
Bangladesh 58 v West Indies Dhaka 04 Mar 2011
Scotland 68 v West Indies Leicester 27 May 1999
Kenya 69 v New Zealand Chennai 20 Feb 2011
Pakistan 74 v England Adelaide 01 Mar 1992
Ireland 77 v Sri Lanka Port Elizabeth 18 Apr 2007
Bermuda 78 v Sri Lanka Port of Spain 15 Mar 2007
Namibia 84 v Pakistan Kimberley 16 Feb 2003