The unidentified assailants came in two cars and opened fire from revolvers on the bus parked outside a college here, police said.
The college and bus is owned by local MLA and All India Congress Committee Secretary Ashwani Sekhri.
They fired atleast 7 rounds on the bus, police said, adding, the assailants later managed to escape towards Amritsar.
A case has been registered in this connection, police said, adding, the reason behind the firing could not be known.
He warned Chief Minister Parkash Singh Badal against alleged laxity asking him to wake up from his slumber and take the incidents seriously lest the situation gets out of control.
"Better nip the evil in the bud", he said, adding, if Badal did not have the will to act, he should better quit.