On Tuesday, witnesses at The Bow reported seeing a man wielding a knife, uttering threats and making references to terrorism.
But by the time police arrived, he had slipped past security and vanished.
Police took no chances and ordered everyone to leave the 58-storey structure by the stairs.
Later in the week, police said they had a pretty good idea of who they were looking for, saying it was someone who suffered mental health problems and was known to police.
On Thursday, officers were called to the Westin Hotel for a complaint about an unwanted guest and arrested Tyler Judin Berg.
(CHQR)Suggest a correction