Characterization of simple symplectic groups of degree 4 over locally finite fields of characteristic 2 in the class of periodic groups

Suppose that each finite subgroup of even order of a periodic group containing an element of order 2 lies in a subgroup isomorphic to a simple symplectic group of degree 4 over some finite field of characteristic 2. We prove that in that case the group is isomorphic to a simple symplectic group S₄(Q) over some locally finite field Q of characteristic 2.