I am shocked at the presumed guilt based on what we know about this situation so far:
The only thing we (on the Think Tank) have been told is that a female employee was sent text messages and called by voice phone by a male employee and asked her out. Asking out a colleague is NOT sexual harassment in the eyes of any law that I am aware of (if it is, almost the whole human race is probably engaging in criminal activity), and in many small businesses it is the start of long and wonderful relationships.
Even doing so repeatedly does not fit the definition of sexual harassment. It could eventually be grounds for stalking or depending on the actions or words other cimes, but that is a different discussion. In order to qualify for sexual harassment according to the law the employee must feel as thought their job, wages, hours, evaluations, etc. will be affected by their refusal or acceptance of the offer being made.
It may even qualify for sexual harassment if the proposals are done on the clock and interfer with the employee’s comfort in the workplace, but this starts to get into grey areas.
The next tier of severity to be examined is did the employee who was being the aggressor violate any of your company policies, particularly as they pertain to fraternization. Typically a business will create policy dictating proper conduct between employees who come from different parts of the chain of command in order to guard against their exposure to the grey areas mentioned above. Many of the persons posting here have insisted that the employees actions would be in violation of their policies, however I am guessing since you had to ask and post the question here that you do not have a specific WRITTEN policy against fraternization.
In summary, the details of the scenario so far seem insufficient to prove that this GM was indeed in violation of the lawful definition by asking out a fellow employee. Further, unless you have WRITTEN policies governing fraternization, employees of any position are welcome to ask out any other employee - whether this is wise for them or not is another matter.
In order to fully evaluate this situation you must obtain more information from BOTH employees involved! If after getting the story from both employees, you feel that the GM abused his position (such as offering or implying promotions, pick of hours, etc.) in his interaction with the female employee and violated the textbook definition of sexual harassment then you need to document every piece of evidence and let this employee go. This should not require a lawyer at this time, you are clearly backed by the law.
If after getting all of the details you feel the employee violated rules of your business (or the way you want to run your business), then I would also recommend letting this employee go, but here is where grey areas begin and it may be adviseable to consult an attorney to make sure you are not violating any unlawful termination laws yourself.
Finally, if you find the GM did nothing more than send text messages and/or verbally ask a female employee out as it has been described so far then you cannot fire him for that without a policy in place! If this strikes you as improper behavior for your GM to be interacting in, you may need to establish a WRITTEN policy for it (possibly with the advice of an labor relations attorney or human resources persons), explain that policy to the GM and you can then enforce it going forward.
As a store owner I personally encourage employees (even those at different places in the chain of command) to hang out together, date, and even marry. As stated above I think the workplace is one great place to get to know a potential mate. I have had many couples meet and have great relationships as well as even some marriages.
I do however establish other code of professional conduct and it is clear that couples private life is their own and does not belong in my store and cannot affect my operations. Further, I strictly enforce immediate dismissal of anyone who violates the textbook sexual harassment definition I have outlined here.
I think this GM clearly exhibited poor judgement by creating this situation while still in a probabionary period, but let’s not criminialize his activity until we have done our homework, heard both sides of the story and clearly defined what rule(s) he has broken.