Conversation so far:
Did Claudius assassinate Caligula?
On 24 January 41, Caligula was assassinated in a broad-based conspiracy involving the Praetorian commander Cassius Chaerea and several senators.
How was Claudius involved in the assassination of Caligula?
There is no evidence that Claudius had a direct hand in the assassination, although it has been argued that he knew about the plot
What happened with Claudius after the murder of Caligula?
In the chaos following the murder, Claudius witnessed the German guard cut down several uninvolved noblemen, including many of his friends.
Did Claudius do anything to stop the German guard who was cutting down several uninvolved noblemen, including many of his friends?
He fled to the palace to hide.
What happened after Claudius hid from the German guard?
According to tradition, a Praetorian named Gratus found him hiding behind a curtain and suddenly declared him princeps.
Did Claudius rule Rome?
When they heard of the Praetorians' claim, they demanded that Claudius be delivered to them for approval, but he refused. Eventually the Senate was forced to give in.

Question: What happened after Gratus found him?
Self-contained rewrite: What happened after Gratus found Claudius?