Was the Ripper motivated by sexual sadism? If not, what was the behavioral motive for the assault?

You have heard that there is a serial rapist in London who is known as the Ripper Copycat. You found out that a colleague of yours from London is on the investigation team for this serial rapist. Your colleague has e-mailed you and asked if you were familiar with Jack the Ripper if you have any information on the following:

• Was the Ripper motivated by sexual sadism? If not, what was the behavioral motive for the assault?
• Why was the Ripper targeting prostitutes?
• What were the Ripper's signature behavior(s)?
• Why did the Ripper stop?