At least 18 people were killed, and 57 other victims injured in mass shootings across the US over the weekend, according to data from a monitor published on Monday.

The Gun Violence Archive research group documented 10 mass shootings from Saturday through Sunday in eight states, including Arizona, Michigan, Nevada, New York, Pennsylvania, South Carolina, and Tennessee.

It defines mass shootings as having "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."

The highest casualties were reported in Philadelphia, Pennsylvania when three people were killed and 12 injured after gunmen opened fire in the bustling South Street neighborhood on Saturday. Police believe the shooting may have stemmed from a fight nearby recorded on bystander video. No suspects have been taken into custody.

“Horrendous and unthinkable acts happened in a very popular local and tourist hangout that claimed the lives of three people and injured 12 others on Saturday at approximately 11.31 p.m. local time (0331GMT Sunday),” Philadelphia Police Department Commissioner Danielle Outlaw told reporters Sunday.

“Multiple Philadelphia police officers were stationed on South Street when they heard multiple gunshots coming from the area 400 South Street,” the commissioner said.

In Chattanooga, Tennessee at least 2 people were killed and 12 others injured outside of a nightclub early Sunday morning. At least one victim was killed when they were hit by a vehicle attempting to flee the scene.

The Gun Violence Archive tallied over 18,600 gun violence-related deaths this year, more than 10,000 of which have been ruled suicides.

The monitor has cataloged 246 mass shootings, including 12 mass murders, in 35 states and Washington, D.C./aa