What triggered Salman-Bishnoi gang feud, and how did it escalate over 28 years?

The feud between Salman Khan and Lawrence Bishnoi's gang dates back to 1998, when two blackbucks were allegedly killed during shooting of 'Hum Saath-Saath Hain'. Khan was among those accused. The gang has repeatedly threatened Salman, citing animal's religious significance. The gang claimed responsibility for attack on Tiger Shroff on Sunday and threatened to kill others who work with Salman.