The activist identified as Randhir Singh Dheera from Ludhiana, had come here to protest the construction of a colony by one Deedar Singh, they said.
Dheera claimed the ownership of the land on which the colony was being developed by Singh, police said.
When Dheera came to know about the construction, he and his few accomplices fired at Singh's family yesterday.
No one was injured in the incident, SSP Fatehgarh Sahib, Hardayal Singh Mann said.
