Not sure what he did, but he is charged under California Penal Code 273.5
(Corporal Injury on a Spouse, Cohabitant, or Fellow Parent)
http://law.onecle.com/california/penal/273.5.html
273.5. (a) Any person who willfully inflicts upon a person who is
his or her spouse, former spouse, cohabitant, former cohabitant, or
the mother or father of his or her child, corporal injury resulting
in a traumatic condition, is guilty of a felony, and upon conviction
thereof shall be punished by imprisonment in the state prison for
two, three, or four years, or in a county jail for not more than one
year, or by a fine of up to six thousand dollars ($6,000) or by both
that fine and imprisonment.....
.