Sun is our need to feel whole and complete inside ourselves. In Scorpio, the style of behaviors that produce this will be intense, regardless of the actual behavior.
This works well for him IF his Sun is well-aspected to the other 9 planets. And it works poorly for him IF his Sun is badly-aspected to the other 9 planets ... unless he has outgrown this inner conflict shown by the aspects.
A well aspected Sun in Scorpio brings out the positive side of Scorpio style .. and badly aspected brings out the negative side.
Our Rising Sign is the social mask we hide behind when we are in a social setting where we are not yet comfortable and relaxed. So Capricorn Rising will be shy/quiet/withdrawn UNTIL they become relaxed in the situation.
Mars in Capricorn depends HUGELY on HOW Mars aspects other planets. Well-aspected, your needs and the action you take to meet your needs, will be well thought out ahead of time, practical, realistic. Badly-aspected, you have a poor sense of timing goals don't work out well for you, or you may feel guilty about having wants/needs (which interferes with success). Or may have trouble handling frustration and feel guilty over irritability/anger, or afraid TO be assertive.
In the 1st house, your Mars/action nature is part OF your social mask, so when others meet you, this is is the part of you that they DO see, that you cannot hide (each planet represents part of our true inner self, and the 1st house represents what we allow others to see of us)