kevin is within his legal rights. the home is in the state of illinois which has multiple statutes that work to form a 'castle doctrine'. here's how it reads-
Defense of a dwelling
The next statute covers use of force in defense of a home. “A person is justified in the use of force against another when and to the extent that he reasonably believes that such conduct is necessary to prevent or terminate such other’s unlawful entry into or attack upon a dwelling.” 720 ILCS 5/7-2(a). This section then defines that deadly force is justified only if, “(1) The entry is made or attempted in a violent, riotous, or tumultuous manner, and he reasonably believes that such force is necessary to prevent an assault upon, or offer of personal violence to, him or another then in the dwelling, or (2) He reasonably believes that such force is necessary to prevent the commission of a felony in the dwelling.” 720 ILCS 5/7-2(a)(1), 720 ILCS 5/7-2(a)(2).
so kevin actually could have used deadly force b/c breaking and entering is a felony in illinois.