Police are investigating a terrorist attack outside a north London mosque after a van drove into a crowd of people, leaving one man dead and several others injured.

The crash happened when the area was crowded with people leaving the Finsbury Park mosque after Ramadan prayers.

“Sadly, Londoners are waking up to news of another dreadful incident in the capital that has left a number of people seriously injured,” said Neil Basu, Sr. National Coordinator for Counter-Terrorism Policing. “This was an attack on London and all Londoners and we should all stand together against extremists – whatever their cause.”

U.K. Prime Minister Theresa May held a press conference early Monday and described the attack as a “sickening” attempt to destroy liberties that unite Britain, such as freedom of worship.

May says the man who plowed a van into a crowd of people leaving evening prayers acted alone and that people outside the mosque apprehended him.