We innovate the Lorentz covariant spacetime curls for the complex Minkowski space, from which the extended Maxwell equations are theoretically derived rigorously. The extended Maxwell equations, which actually arise from the features of the spacetime characterized by the Lorentz transformation, are found to be capable of describing the fields of electromagnetism and weak gravity as distinct solutions in the unified way. The properties of gravitational and electromagnetic fields, such as the interaction force, the energy flux density and the Lagrangian, are obtained homogeneously. The nature that the electric charges with the same sign repel each other and the objects with masses always attract each other, which was previously considered to be the bounty of nature, can now be theoretically derived in this mechanic. Besides, both the electromagnetism and the gravity unfold their mirror descriptions. A unified charge dimension, which will facilitate to the homogeneous description of the two interactions, is proposed. The mechanic is partially examined in a thought experiment.