Lifting weights in -season should not hurt your shooting as long as you maintain flexibility (by stretching) as well. Strength training will not only improve your shot (by giving you a stronger body to keep yourself in optimal shooting position) but can also help you avoid injury and be a better overall athlete.
Weight training basically causes small injuries to your muscles that, with good nutrition and time to recover, helps your muscles work better and grow even stronger. Make sure you follow a program that's going to help your game and not just one that's going to make you look more buff.
You should find a local athletic trainer who can teach you about "periodization" which is a way to train that maximizes your body's improvement in strength to help you "peak" at the right time.
Most trainers suggest more weight training (3-4 times a week) in the off-season and less frequent weight training (1-2 times/week) during the season, alternating the muscle groups you train (more upper body work on one day, more lower body work the next).
Hope this helps.