Airbag

Today my father was driving my 525i down the road to take my sister to softball tourniment and he hit a bump and the airbag deployed on him for no reason. Now do i need to replace the whole airbag to get the srs light to go off or can i buy an aftermarket steering wheel and use that and disconnect all the airbag shit. Im definatly not putting another one in there after my father burned his whole arm this morning from it. Any ideas why it could have popped out like that too?

Thanks everyone

frayed positive and ground wires somewhere in the harness, them 2 rubbing together set off the bag.
Or
somebody spilled a liquid onto the air bag control moduel under the center consol causing it to short out

my father was driving on a dirt road and it just randomly deployed on him