How was the escape of the convicts announced in Great Expectations by Charles Dickens?

As Pip and Herbert help in Magwitch's escape by boat, they are overtaken by the police, who have with them their informant, Compeyson, Magwitch's old nemisis. Magwitch lunges for him and they both fall into the river; Magwitch stubbornly clings to Compeyson, drowning him, while risking his own life. Magwitch is pulled from the river, arrested and taken to prison, where he dies, probably of pneumonia.