The football player admitted to police that on the night of the murder, he and Breana had been arguing about the pregnancy.
According to court documents, Trejo claimed that Breana had waited 'too long to tell him about the pregnancy to get an abortion'.
When asked by police what he did about that, Trejo answered 'I took action... I took her life'.
Trejo confessed to police that he had murdered by Breana by stabbing her in the heart with a knife, before stuffing her body into a plastic bag and tossing it into a rubbish bin behind a restaurant.
Speaking to The Daily Beast, Trejo's aunt Alexzaundra Patton-Manu said it was 'not his character' to have committed such crimes.
Trejo is due to be sentenced in January next year where he reportedly faces up to 80 years in prison.