The fact is that making it harder for someone to legally buy a gun for legitimate, non-harmful purposes (assuming there are any) does not make it harder for someone to acquire a gun illegally.
But, of course, bombs are more dangerous than guns. The concerning thing is that you can buy all of the components to make an effective explosive device at any hardware store. It may cost less money overall, there's the potential to kill more people, and the attacker doesn't have to be anywhere nearby when it happens. The attacker's name would never get on any list of gun owners, s/he wouldn't have to wait X number of days but could start immediately, and s/he can still buy all of the components whether s/he's been to prison before or not.
The irony is that, of all the people wanting to kill a bunch of other people, people tend to prefer guns. (Maybe that's a good thing.)
Thinking of the specific situation, the university and involved law enforcement did not handle the situation well. Two people were killed and they assumed the attacker had left or was one of the dead. Presumably, he took a leisurely stroll across campus (half a mile in 2 hours is pretty leisurely) before killing more. Not only was the law enforcement ineffective, but the university didn't bother to tell anyone what was going on until 2 hours after the first killings, when it was already too late.
You also have the fact that, according to the media, people were concerned about the guy. According to one source, he was just your typical homicidal maniac (paraphrased, of course). Apparently, the fact that he never talked to anyone (saying a few evasive words is not talking) wasn't concerning enough.
You get the idea that maybe someone screwed up with this kid beyond the point where "more gun control" would do a damned thing. (And of course "more gun control" is kind of late now. The people are already dead.)
