A scuffle broke out on a Southern California beach where President Donald Trump supporters were marching as counter-protesters doused organizers with pepper spray, authorities said Saturday.

The violence erupted when the march of about 2,000 people at Bolsa Chica State Beach reached a group of about 30 counter-protesters, some of whom began spraying the irritant, said Capt. Kevin Pearsall of the California State Parks Police.

Three people were arrested on suspicion of illegal use of pepper spray and a fourth person was arrested on suspicion of assault and battery, Pearsall said.

Pearsall added that two people had suffered minor injuries, not requiring medical attention.

One anti-Trump protester who allegedly used the eye irritant was kicked and punched in the sand by Trump supporters, according to the Los Angeles Times.

Before the march started the counter-protesters had said they intended to try and stop the march’s progress with the use of a “human wall.”

The Associated Press contributed to this report.

