No, because the 18th century was more violent than life today, not less
The problem with this hypothetical is that it assumes that "gun violence" was not prevalent in the 18th century, and if it was, that the idea of a lone crazy gunman would be so especially horrifying that the founders might have decided that allowing private ownership of firearms would be a bad idea. While it is not wrong to be horrified by lone gunmen, a large part of why we are today is because acts of violence are less common in our modern society than they used to be for most of the people living in it.
There were very few police in 1787
Modern policing as we understand it today is largely a product of the early-to-mid 19th century. The primary law enforcement official in colonial and pre-industrial America was the local sheriff. The sheriff would investigate crimes and arrest people, but he generally did not operate a large number of deputies doing the sort of anti-crime patrol that modern police departments see as their primary responsibility. This has two consequences.
The first is that there is simply more crime; we cannot say exactly how much more because it was before modern crime statistics were invented.
The second consequence is that defending yourself from violence is your individual problem to deal with most of the time. If you live in 1787 and someone is going to use a weapon to harm or kill you, you are almost totally on your own in dealing with this problem. There is no one else to call for help. You can't even "call" for help; the telephone wasn't invented yet. You're going to have to deal with it yourself, which means you're probably going to want the legal right to arm yourself with potentially anything even if you'd rather not.
If you are lucky, you might be living in a place with community minded people and therefore might have some sort of volunteer town watch just to make sure nothing especially bad is happening and that no buildings are on fire (there was also no fire department). So, maybe this could be a source of help in stopping some crazy lone gunman. But, the problem here is that these are other people who are ordinary citizens just like you; they're not a part of the government. So... they're going to want the Second Amendment written exactly as it is today also.
There were sources of violence in the 18th century that we don't have to deal with today
The biggest supplier of gun violence in the 18th century were the armed forces of the British Empire. Even if we set aside the Revolutionary War and the War of 1812 as times where you'd want to be armed, the British Navy used to stop ships at sea and kidnap all of the people on them in order to be sailors on their own ships. This was called impressment and the British didn't formally end the practice until 1815. You know why the British were able to do this? Because they had big ships with guns on them. Do you what prevents people from doing this to your ship at sea? If you have your own guns on your own ship and look like you're going to use them. Contrary to recent opinions offered by the President, purchasing cannons was allowed by the Second Amendment and was often a practical way to get people to leave you alone on the high seas.
Speaking of being left alone on the high seas, piracy is another source of violence we don't have to deal with anymore.
We also don't have to deal with raids by Native Americans.
All of these are sources of violence that are things individuals needed to defend themselves against because the institutions that deal with them today didn't exist or were not yet capable of dealing with them. When there's no existing alternative to arming yourself for defensive purposes, people are not going to want to entertain the notion that they shouldn't be allowed to arm themselves.