(CNN) -- Last night's shooting rampage at a movie theater in Aurora, Colorado, was a nightmare. Authorities have already arrested a suspect. Four weapons were recovered in the shooting scene, including a shotgun and two handguns. Twelve people have been killed, with many more injured. According to law enforcement officials, the weapons were purchased legally by the suspect in the last six months.

The shooting was senseless. And it makes us think once again about how we can address the horrific problem of gun violence in America.