Tomcat valve JAAS : form error page displayed first before response reaches back to Tomcat valve

Using form-based authentication.

1. web.xml

<login-config>
<auth-method>FORM</auth-method>
<form-login-config>
  <form-login-page>/login.jsp</form-login-page>
  <form-error-page>/login-redirect-error.jsp?error=true</form-error-page>
</form-login-config>
</login-config>

2. Custom valve and defined in META-INF/context.xml

public class SecurityValve extends ValveBase {

public void invoke(Request request, Response response) throws IOException, ServletException {
    getNext().invoke(request, response);   
    system.out.println("after getNext()"); --> break point (BP)
}

}

Understanding of flow:
1. request --> valve --> JAAS --> Filter --> Servlet/JSP
2. response <-- valve <-- JAAS <-- Filter <-- Servlet/JSP

What i noticed:
1. Did a break point on SecurityValve (indicated at BP)
2. On forms, i purposely enter wrong credential and submit
3. Break point stops at BP
4. login-redirect-error.jsp displayed already
5. Since it stop at break point BP in SecurityValve, the response back to client flow has not reached the browser. Yet the login-redirect-error.jsp is already displayed

Question:
How can the login-redirect-error.jsp be displayed on the browser when the response flowing back to client stop at break point BP? The flow back to the client is not fully done yet.