It was a warm April evening, much warmer than it should have been, and the sun was coming down slowly over Chicago Avenue. Waiting at Milwaukee for the light to change, I argued with my girlfriend about which way to head on our bikes.

“Let’s go west for a change,” she said.

“But we haven’t been down to the lake since it’s gotten warm,” I replied insistently.

Just then the light changed, and I took off going east on Chicago before she had a chance to speak again. A few moments later I heard the sound of hoofs on asphalt behind me, moving fast. Looking back I saw a horse and carriage, the kind tourists like to take in the summer, coming up behind my girlfriend. But something was definitely wrong. The horse was running at a full gallop, and the carriage driver, a petite young woman, was madly pulling on the reins and screaming something about a dog at the top of her lungs. At that point I noticed a brown pit bull coming full bore down the street behind the carriage, mouth foaming, chasing the horse intently, with no sign of giving up.

My first reaction was to get the hell out of the way and to make sure my girlfriend did the same. As the surreal scene flew by, missing us only by a few feet, I realized that if I could stop the dog there was a possibility the horse might slow down. If it didn’t, a collision with a car or a pedestrian was imminent.

I sped up to try to head off the dog with my bike, but the dog had too much of a lead on me. The next thing I knew the horse and carriage were bouncing off a parked car just west of Halsted. The horse broke free of the carriage and continued to gallop wildly down Chicago, while the driver flew off the carriage into the air, landing on a parked car.

As my girlfriend and I rode up to help her, I was relieved to see that the driver was standing up, though her mouth was bloody and a few teeth were loose or missing. As my girlfriend comforted her, people began to wander up, cell phones in hand, ready to call for help. The driver was eventually taken away in an ambulance.

The dog’s owner was cited, I learned later, and the horse was subdued by 18th District tactical officers somewhere near Franklin. “He was a domestic animal, so the officers were able to cordon him off and calm him down,” said Sergeant Robert Cargie of the Chicago Police Department. “By then he was pretty tired out.”