If they hadn’t already had to, a couple celebrating 50 years of marriage with family and friends is now being called to make good on the “in sickness and in health” portion of their wedding vows: Someone sprayed a mace-like substance into the yard where the anniversary party was taking place around 11pm in Chicago Saturday, and ambulances lined up along the block to treat the 23 injured, many of them kids.

A Chicago Fire Department spokesperson said no one suffered respiratory stress, only mild skin irritation, and all of the injured were released from hospitals overnight, reports the Chicago Tribune.

One family member questioned at the scene said it remained unclear why anyone would spray guests at the party. No one is in custody yet, reports CBS Chicago.

The couple and guests had been celebrating outdoors at a home in Chicago’s Gage Park area. (At a New Jersey wedding last month, 300 guests ended up in a brawl that got police called.)