Ok, I’m calling bullshit. There were 27 mass shooting events with >= 4 dead in the US in 2018:
https://en.m.wikipedia.org/wiki/List_of_mass_shootings_in_th...
(I used 4 dead as the cutoff, since it is close to the mean in the article’s data set.)
If you count people that managed to shoot at least 4 others, then there were 323 attempted serial murders, “resulting in 387 deaths and 1,283 injuries, for a total of 1,670 victims.”
The article may as well be titled “Serial murders can mow be performed in under an hour, thanks to improved technology”
Having said that, you are right - technology might be better at finding and stopping serial killers, but doesn't really do much at all for finding and stopping parallel killers. Mass killing is way up, so the article's conclusion is not really all that reassuring.