A 97-year-old woman was targeted by thugs who went on the rampage at a sheltered housing block in Chorley.
Vandals damaged six cars and five properties during their spree at Richmond Court on Pall Mall on Sunday.
Police say the oldest victim was 97 and in one incident, a flower pot was thrown with such force that it smashed a bathroom window and broke both the bath and toilet system.
Cars parked in the communal parking area were damaged, as well as cars on nearby Duke Street.
Sgt Andy Bramhall, of Chorley Police, said: “This is sheltered accommodation – these elderly people want a quiet life.
“It has obviously been a distressing experience for them and we are working closely with Richmond House to offer reassurance.
“We have had to do a lot of work with residents to reassure them we are doing all we can to catch the person responsible. Forensics have been found at the scene.”
A rotary washing line was also forced from the ground during the incident, which happened at around 5.20am on Sunday.
Richmond Court is managed by the Leeds-based Accent Foundation.
Communication co-ordinator Heather Jacklin said: “We were extremely concerned to hear of this thoughtless violent act and our staff are working with the police to reassure residents and provide any support that may be required.
“We own and manage the homes at Richmond Court and Richmond House which are sheltered flats for older people.
“In the early hours of Sunday morning windows to the communal lounge and two of the flats were damaged by vandals.
“Our emergency repairs contractor attended to board up the windows and make the flats secure.
“We have placed repair orders to re-glaze the damaged windows and replaced a toilet and bath that were damaged in the incident.
“This work should be completed by early next week.
“Our scheme manager was on duty on Sunday morning to support residents and help the police with their enquiries.”
Police have urged anyone who may have any information to come forward.
Call police on 101 or Crimestoppers anonymously on 0800 555 111.