In Skyrim, I only pickpocket bandits (basically to raise my skill level with no chance of detrimental effects), and only right before I kill them. However, when I left a bandits' hideout recently, there were thugs waiting outside with a contract signed by a bandit. Is the lag between pickpocketing and killing enough that the bandit could have hired a thug?
Even if the NPC is dead, he or she will still send thugs. Actually the game just puts a random NPC name in the contract. Thugs are sent to kill you because you probally stole things. So far I completed the Hermause Mora Quest of Septimus is gone but a few days later I killed some thugs and there was a note from him. However if you never stole anything and thugs are still after you, then steal stuff and then thugs will kill you and then I will be fixed.