Scotland’s Parliament suspended its second and final day of debate on whether to hold a second independence referendum, following reports of a terrorist attack Wednesday in London.

It will now vote for or against holding a referendum on Tuesday ― the day before the British government is due to trigger the United Kingdom’s divorce proceedings with the European Union.

Politicians had been debating when the attack happened outside the U.K. Houses of Parliament. At least four people died and 40 were injured when a driver mowed down pedestrians on London’s crowded Westminster Bridge before trying to storm the Parliament. The attacker and a police officer are among the dead, authorities reported. Parliament remained under lockdown while a police operation was taking place.

Scottish First Minister Nicola Sturgeon tweeted her condolences shortly after the “dreadful incident” was reported.

My thoughts are with everyone in and around Westminster caught up in this dreadful incident - and with the brave emergency services. — Nicola Sturgeon (@NicolaSturgeon) March 22, 2017

Sturgeon has been rallying support for a second vote on Scottish secession from the United Kingdom before March 2019, when the U.K. is due to exit the European Union. Two-thirds of Scottish voters had voted against a Brexit in June 2016.

Scots rejected independence during an earlier plebiscite in 2014.

To hold another referendum, Sturgeon would require backing from the Scottish Parliament in the Holyrood area of Edinburgh before she could seek the required legislative authority from Westminster.

The initial parliamentary vote was set for Wednesday.

The first minister said she “fully supports” the postponement in light of the attack in London.

“This was not because of any specific threat to the parliament or to Scotland,” she noted. “We are liaising with our counterparts in the U.K. government, and the Scottish government stands ready to support in any way we can.”

British Prime Minister Theresa May is firmly opposed to the vote, and has stressed the need for the U.K. to be “working together, not pulling apart.”

Read more about the referendum bid here.

This article has been updated with more details including the new date for the debate and the revised death toll from police.