Would gun regulation decrease violence across the board?

I subscribe to weekly emails from the White House. I just opened my inbox and found this week’s email. It was all about the need to pass a gun control bill, “to make the world safer for our kids.”
Two things come to mind instantly when I read this. One is the Schaffhausen case. I don’t know what kind of coverage this is getting nationally, but here, just across the border in Minnesota, it’s a huge deal. You can’t watch the evening news without hearing this guy’s name at least once or twice. What kind of laws could have prevented this horrible crime?
The other thing that comes to mind is the Boston Marathon bombing. No guns were used, but it was just as bad as or worse than the mass shootings that have taken place recently. What kind of laws could have prevented this horrible crime?

Yes, removing guns from the public’s possession may reduce the number of domestic shootings and accidents. But what about stabbings and bombings? Other violence?

I’m at a loss to understand how gun control laws alone will decrease all kinds of violence. I’m looking to my fellow jellies to explain the thought process to me. Any statistics of stabbings and bombings in other countries with gun control policies in place would be appreciated. If the statistics seem to indicate that these policies have worked this way, would you care to give a theory as to why?