Millions voted for the United Kingdom to leave the European Union in Thursday's historic referendum known as Brexit, but some voters on Friday expressed shock after finding themselves on the winning side and watching the U.K. start to withdraw from the bloc.

The campaign to leave the EU won with 52 percent of the vote, and the national election produced a high turnout, with 72 percent of the more than 46 million registered voters casting a ballot. On Friday, Prime Minister David Cameron, who campaigned to remain in the EU, said that he would resign, and the vote has sent shockwaves throughout the global financial markets.

One voter told the BBC that he didn't think his vote to leave the EU would matter.

"I'm a bit shocked to be honest," the voter, identified as Adam from Manchester, England, told the broadcaster. "I'm shocked about both. I'm shocked that we actually voted to leave. I didn't think that was going to happen. My vote, I didn't think, was going to matter too much because I thought we were just going to remain."

Adam from Manchester voted for LEAVE. He is "shocked & worried" by country's decision to Brexit. Don't be like Adam. pic.twitter.com/oAbjGVHdA0 — The Greek Analyst (@GreekAnalyst) June 24, 2016

He also didn't expect Cameron to resign: "The David Cameron resignation has blown me away to be honest. I think it's been- the period of uncertainty that we're going to have for the next couple of months, I think that's just been magnified now. So, yeah, quite worried."

Adam may not be alone.

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After the result was announced, the top question on the EU that was asked on Google in the U.K. was "What does it mean to leave the EU?" the company said on Twitter.

The second top question: "What is the EU?"

"What is the EU?" is the second top UK question on the EU since the #EURefResults were officially announced pic.twitter.com/1q4VAX3qcm — GoogleTrends (@GoogleTrends) June 24, 2016

Another voter told British broadcaster ITV that she was "really disappointed about the results" even though she voted for leaving the EU.

"This morning, I woke up and the reality did actually hit me," the voter, identified as Mandy, told ITV. "But if I had the opportunity to vote again, it would be to stay."

Time found other voters on Twitter who expressed regret over their votes to leave.

Urm I think I kinda regret my vote, I had no real reason to pick what I did!! — Tom Walker (@thomaswalker93) June 24, 2016

I personally voted leave believing these lies and I regret it more than anything, I feel genuinely robbed of my vote😡😤😭 — gibbo (@rambogiblet) June 24, 2016

On Friday, an effort was launched to give them and other voters another chance. An online petition to Parliament asked for a second referendum, noting that neither side received 60 percent of the vote and that turnout was less than 75 percent.

As of Friday night in the U.K., the petition received more than 160,000 signatures, requiring Parliament to consider the measure for debate.

British newspaper The Independent, which reported that the petition site was "completely inaccessible" at one point during the day, noted: "Of course, a second referendum would almost certainly be rejected, as referenda are not the sort of thing you get a second crack at."