Deepak Kakade, 21, tried to pull the gold chain of one Lata Patil while she was walking near a temple in Dombivili at around 9 PM yesterday, police inspector Vilas Jadhav said.
As the woman raised an alarm, the passersby including Lata's relative Ajay Chowdhari, chased the culprit who tried to flee in an autorickshaw.
When the angry crowd tried to stop the autorickshaw, Kakade allegedly attacked Chowdhari with a sickle and even the vehicle driver attempted to mow down the people.
In retaliation, Chowdhari allegedly fired at Kakade from his personal revolver.
Kakade was admitted to Sion hospital in Mumbai and is reported to be serious, police said.
Search for the autorickshaw driver is on, police said, adding that a case has been registered in the incident.