I've been Stealthing Bank Heist: Money with my friends and all of a sudden a bulldozer decided to come in. I can't find any info about why this is happened, nor I could replicate this. Does anyone know why did he spawned? Now I really wanna know it...

I've been Stealthing Bank Heist: Money with my friends and all of a sudden a bulldozer decided to come in. I can't find any info about why this is happened, nor I could replicate this. Does anyone know why did he spawned? Now I really wanna know it...