The incident took place on Friday morning at around 8am in Leyland.
Officers now think the attack was linked to a second incident, which happened around an hour later in Chorley, where again, an elderly man has been targeted and was forced to withdraw money and hand it over to an offender.
Police say they have arrested four people, one at the scene and three in Blackburn, on suspicion of aggrevated burglary.
Chief Inspector Chris Abbott from the Chorley and South Ribble Neighbourhood Policing Team said: "You may have heard about an incident on Balshaw Crescent, Leyland this morning or you might see our mobile police station parked up there today and so we want to let you know what has happened and what we are doing about it.