Needs more info. What kind of field? Commercial, government? What kind of contractual obligations apply with the employment? It sounds like a conflict of interest, but outside of government and select industry, that's going to come down to the agreements he made between the employer.
If a private employer doesn't prohibit an employee from awarding bids to the employee's company, and they aren't doing e.g. federal (or municipal or state contracting) it's very likely only an ethics problem. A private employer is ordinarily not required to bid at all prior to awarding work, and by far and large, can hire any company they want, whether or not an employee also owns it.
And outside of government, even if the employer prohibits the behavior, it's most likely a civil issue at best. The most you'd see is likely termination.