Unless there is an employment agreement, a collective bargaining agreement, or unlawful discrimination, most employment is considered "at will." From what I understand, Texas goes even a bit farther than some other states, in finding that the presumption of "at will" employment is not overcome merely by the existence of an employment agreement.
Thus, unless one of the protections listed above may apply to you, your employer is free to fire you.
Frankly, I'm a bit mystified by the penchant of otherwise reasonable adults to be so eager to call the police to report either minor infractions or mere incivility. If I'm correctly understanding you, you called the police to report unlawful parking, and your employer threatened to call the police for your using an unpleasant tone a1nd a harsh word.
Your question did not precisely state that you were fired; instead, you asked whether you could get fired. The answer is yes.
The best advice I could give you is to try to conduct yourself in your employer's presence in a pleasant and civil manner and not to get too concerned about illegal parking.
Good luck to you.
As an at-will employee, you can quit at any time for any reason, you can be fired for any reason, a rotten reason, or no reason, except unlawful discrimination. If you do not have an employment contract or union to represent you, your recourse is limited. Discrimination based on age, gender, race, religious beliefs etc.... may give rise to a different answer.
You might find my Legal Guide helpful "Workplace Discrimination: A Basis for Wrongful Termination Claims"
You might find my Legal Guide helpful "How to Choose a Lawyer for you.”
You might find my Legal Guide helpful "What Do I Tell My Lawyer"?
No one can know what the record is in the case because online we cannot find out any details. Check with a lawyer in your locale to discuss more of the details.
If you have a discrimination theory about retaliatory discharge or hostile workplace conditions you'll need a lawyer. Religious belief, age, gender, race etc. all are discriminatory reasons for which you cannot be legally fired and upon which you might base a wrongful termination suit.
Good luck to you.
NOTE: This answer is made available by the out-of-state lawyer for educational purposes only. This observation is not like a communication with a lawyer with whom you have an attorney-client relationship along with all the privileges that relationship provides.