Four people were killed on Friday in a shooting at a Montana bar, prompting a lockdown in a neighborhood several miles away as authorities searched a wooded area for a suspect in the case.

The shooting brought the number of mass murders so far this year in the US to nine, according to the Gun Violence Archive, a non-partisan resource which defines such cases as killings in which four or more victims are killed.

All those mass murders were shootings, and four have occurred in a 30-day period beginning 2 July. It was the US’s second mass murder since Monday, when a man attacked a New York City skyscraper housing the National Football League’s headquarters and shot four people dead before dying by suicide.