>> after trooper davis's portraits have been trimmed, signed, and shipped, a copy will be added to the wall of heroes. that's castro's personal memorial that continues to grow. >> even when i start working on one, you will see identification that another was killed somewhere else. >> the biggest challenge for castro is keeping up. sketching two or three officers a week. >> unfortunately there is always going to be an officer to do. >> that's the sad reality. castro will always have an inspiration for his next piece. what an important heartfelt memory. what does former treasury secretary larry summers think about the republican tax plan. why he calls it a serious policy error. that's next.