If he came on the scene *afer* the police got there, certainly. But if he or she (I've got daughters who are often on college campuses, and my wife is a professor) were on the scene when the shooting started, or even when the second episode started, there would be a whole bunch more people alive.
The Texas Tower shooter, in 1996, was armed with much more powerful weapons, a 0.35 Remington rifle, a scoped 6mm Remington rifle, a .357 magnum revolver, a 9 mm Luger, a 12 guage shotgun, a carbine and another pistol. (6 guns all told) And he had a better more secure perch. He killed 16, half as many as this sicko, but the whole thing was over in 96 minutes. He shot (or clubbed with a rifle butt) several people before reaching the top of the tower, thus making his presence known to people outside the tower. Most of that time he was more or less pinned down by students and residents of the area, who had retrieved their own firearms, mostly rifles, from their dorm rooms, houses or apartments, and of course the rack in the back of their pick up trucks. A few police did show up fairly quickly, but they were often armed only with handguns or shotguns, very ineffectual under the circumstances. Four policemen, who were accompanied up the stairs of the tower, by an armed civilian, killed him. One of his shots killed an electrician 500 yards away.
I personally heard one of the students, a military veteran and, IIRC, a reservist at the time, relate retrieving his M-1 Carbine, talking the Librarian into opening the door to the landing (she didn't care about the gun, but students were not supposed to be allowed out there. :). He said a policeman came up behind him, said something like "good perch, I'll go find one for myself, carry on". No one on the ground was able to hit him, because of the wall around the platform of the tower, but they did reduce his rate of fire and his options by forcing him to shoot through drain holes in the wall, rather than over the top of it.
Today, especially in Austin, the cop would take time out from helping with the real problem to arrest him for having a gun on campus, discharging a firearm in the city, and so on.
Note also that after the initial shots, many civilians retreived their own weapons and fired upon the tower, keeping the sniper pinned down somewhat. Patched bullet holes from this fire (and that of police) can still be seen today.
Also, Mr. Crum (the civilian) drew the attention of the sniper, which made him turn away from the direction the police were approaching. Although the sniper tried to get his weapon back to shoot at the police, he was unable to do so before being shot. If not for the citizen who bravely accompanied the officers, there might very well have been another police victim—as Officer Martinez came around the corner into the ambush.