I agree, could've been prevented or at least lessened if someone else was packing. here's a blurp that I wrote for a college paper I did on Gun Control:

Those who oppose guns and the right to bear concealed weapons make the simple argument that guns and people equal violent crimes; they do not consider that most of the time guns, when in the right hands, make society safer. The fact is that people intending to commit crime fear getting shot.
Professors James Wright and Peter Rossi, co-authors of the U.S. Justice Department’s three-year study on weapons and criminal violence in America, questioned 1,800 prisoners on issues relating to crime and the carrying of weapons by the public. This is what they found:
• 85 percent agreed that the “smart criminal” will attempt to find out if a potential victim is armed.
• 75 percent felt that burglars avoided occupied dwellings for fear of being shot.
• 60 percent felt that the typical criminal feared being shot by citizens more than he feared being shot by police.
• 80 percent of “handgun predators” had encountered armed citizens.
• 53 percent did not commit a specific crime for fear that the victim was armed.
• 57 percent of “handgun predators” were scared off or shot at by armed victims. (National Rifle Association 146)
By these results we can see that the fear of getting shot is very fresh in the minds of criminals. If the government were to take away that fear by banning weapons then criminals, who would be the only ones with guns, would take action more frequently resulting in more crime. An example of this concept can be illustrated very well by the following stories:
In Orlando, Florida rape skyrocketed from 12.8 per 100,000 citizens in 1965, to 35.9 per 100,000 in 1966. Seeing this as a real problem the Orlando police organized a handgun training program for women of the community. The media gave great coverage over the ordeal and the fact that the women in Orlando were armed and willing to resist attack. The following year the rape rate dropped to 4.1 per 100,000. In other places in Florida the rate actually increased. (National Rife Association 147) Similarly, David Kopel says in “Guns in the Right Hands Make Society Safer” that in Kennesaw, Georgia in 1982 an ordinance was passed requiring every home to have a gun; exceptions were made for people with criminal records, and other similar
situations. Within seven months before the passing of the ordinance, there had been 45 residential burglaries. In the seven months after the ordinance, there were only five. This constituted an 89 percent decline. This figure continued in the following years. It was estimated that even before the ordinance gun ownership patterns were the same. What contributed to the decrease in crime is the publicity surrounding the incident. The media coverage warned criminals of the hazard of burglarizing the homes of armed civilians. The argument of media involvement is much the same with the Florida episode.
Not only does the possession of concealed weapon in the home deter criminals, but the carrying of concealed weapons by law abiding citizens has also been proven to not only deter crime but also to stop the criminal in the act of committing a crime. In his article “Carrying Concealed Weapons Prevents Crime”, John R. Lott Jr. tells some very relevant stories regarding this principle. He speaks of Israel and their reputation for terrorists pulling out automatic weapons and firing at civilians in the public twenty years ago. Eventually Israel got fed up with that behavior and expanded their gun laws to allow all qualified individuals to carry concealed weapons. After awhile, terrorists were experiencing ordinary people pulling pistols on them. From that time on terrorists no longer engaged in these types of public shootings.
On March 13, 1997, seven Israeli girls were shot to death by a soldier while visiting Jordan’s Island of Peace. The Israelis complied with Jordanian requests to leave their weapons behind when they entered the border enclave. If they had not left their weapons parents felt they may have been able to stop the shooting.
During the massive coverage of the school shootings that took place in 1997 and 1998 the media failed to tell how they ended. Two of the four incidents were stopped by a citizen with a gun. In the shootout at a high school in Pearl, Mississippi, which left two students deceased, an assistant principal retrieved a gun from his car and immobilized the shooter while the police
were yet to arrive. The school-related shooting in Pennsylvania, in 1998 left one teacher dead, but was stopped only after a bystander pointed a shotgun at the shooter while he attempted to reload his gun. It took an additional 10 minutes for the police to arrive. Ultimately lives were saved by these prompt responses.