Life threat to Sharif brothers

According to a news item, Mr. Rehman Malik informed Mr. Nawaz Sharif and Mr. Shehbaz Sharif, about threat to their lives from the terrorists. If RM has credible information, why doesn’t he take action against those terrorists; unless he knows the plan is hatched not by the terrorists but by someone else somewhere else? This is a known tactic of the conspirators to create fear in the mind of the targeted opponents and safeguard themselves in case of such happenings which most of the time are framed with their consent. The assassination of Benazir Bhutto is a typical example.