Shootings across the country this weekend could be a preview for a violent summer ahead, experts, community leaders and police are warning.

From Chattanooga, Tenn. to Philadelphia, to Saginaw, Mich., at least 11 people were killed while another 60 were injured in mass shootings during the first weekend in June.

Any given year, the summer months are usually when gun violence is at its worst in the country. “Unfortunately we’re likely to see more of this,” Thomas Abt, a senior fellow with the Council on Criminal Justice, a nonpartisan research organization, tells TIME, arguing that the kinds of mass shootings that occurred over the weekend could continue as the summer days and weeks begin. 

The Gun Violence Archive, which is a nonprofit that collects gun violence data in the country, defines a mass shooting as an incident where four or more victims are shot. So far, there have been 247 mass shootings this year, and 13 over the weekend. There have been nearly 19,000 deaths as a result of firearms in the U.S., which includes more than 8,300 homicides as of June 6.