Five men aged 16 to 18 were injured in a shooting Friday at a park in Greenbelt, Maryland, where hundreds of high school students gathered while skipping school, police said.

One victim is in critical condition and the others are in stable condition, Greenbelt Police Chief Richard Powers said at a news conference.

Powers said police are looking for one suspect but there may be others. A motive has not yet been determined.

“There is absolutely no reason for this to happen. It makes no sense, it’s perpetuated in our society and we have to do something to stop it,” Powers said. “Honestly, it’s maddening.”

There have been 120 such mass shootings in the United States in the first 110 days of this year, according to the Gun Violence Archive, which is defined as an incident in which four or more people are shot or killed, not including the shooter.

Bowers said an estimated 500 to 600 students from at least two high schools gathered at the park on “Senior Skip Day,” a day when students in their final year of high school skip class.

Powers said about 20 police officers gathered unexpectedly on social media before the shooting and were at the scene for about 15 minutes. They are able to provide first aid before the ambulance arrives.

“It could be the difference between someone being able to go to the hospital and not being able to go to the hospital,” Powers said.

Greenbelt is a city of approximately 24,000 people located approximately 13 miles (21 kilometers) northeast of Washington.