Awave of mass shootings over the first weekend of June left nine people dead and at least 64 injured across various American cities, according to the Gun Violence Archive, a website that tracks gun violence incidents nationwide.

While there is no singular consensus on what constitutes a "mass shooting," the Archive defines it as: "a minimum of four victims shot, either injured or killed, not including any shooter who may also have been killed or injured in the incident."

Using that definition, mass shootings took place in Akron, Ohio; Louisville, Kentucky; Newport News, Virginia; Pittsburgh, Pennsylvania; and several other cities between Friday and Sunday. Most of the incidents happened at birthday parties and celebrations, while others occurred inside nightclubs and outside bars.

Newsweek has created a map showing the locations of the weekend shootings.

The shooting with the most casualties happened in Ohio early Sunday, where one person died, and 24 others were injured at a large birthday party. Akron Police Chief Brian Harding reported that the party had over 200 attendees earlier in the night. Police are investigating the circumstances and have not yet made any arrests.

At around the same time, a five-hour drive south in Louisville, Kentucky, six teenagers were injured in a shooting at a party. No fatalies were reported.

In St. Louis, seven people were injured outside a bar near Fairground Park. Despite at least 90 shots being fired, no one was killed.

In Pittsburgh, two people were killed and seven others injured in a shooting at a hookah bar in Penn Hills early Sunday morning.

A separate incident in Columbus, Ohio, resulted in the death of a 39-year-old man and left three others injured in a shooting on the city's east side. No suspects have been identified.

Philadelphia was the scene of at least two shootings over the weekend, leaving at least two people dead and several others injured.

In Rock Hill, South Carolina, a neighborhood block party turned violent with two people killed and two others injured. A 44-year-old woman and a 21-year-old man died at the scene. Police are investigating.

Another celebration in Lower Santan Village, outside Phoenix, Arizona, ended in tragedy when two people died and four were injured during a shooting at a teen birthday party. Tribal officers and civilians were among the injured.

In Detroit, Michigan, at least nine people were shot in two separate shootings on Friday night going into Saturday morning.

These instances of gun violence, over a single weekend at the start of summer — when shootings tend to spike — are among more than 192 mass shootings in the U.S. so far this year, according to the Gun Violence Archive.